Good advice given above already...I'll just sum this up for you...
First of all, your Green Cheek trying to "feed you" is also extremely common and a normal thing for them to do when they are hormonal, just as the moodiness, the nipping, etc. are all common behaviors for them to exhibit when they are hormonal. So it's nothing odd that he's doing. And if he hasn't done this already, be prepared because he may very well also start trying to "mate" with your hand as well. Again, this is totally normal behavior for them when they are hormonal, and it's nothing that you need to worry about. However, there is a "right" way and a "wrong" way to handle this.
***It's extremely important that you don't punish him when he does these hormonal behaviors, because it's not his fault, and you can really do some emotional and psychological damage if you punish him when he starts regurgitating for you or when he starts trying to mate with your hand or your neck. However, you also don't ever want to encourage this behavior in him either, because what can happen is that you send him mixed-signals, like he thinks you're encouraging him to mate with you or to regurgitate for you, so he'll keep doing it, but when it doesn't work the way he wants it to (obviously he can't mate with your hand or your neck, nor is your hand going to accept his feedings), then what will happen is that he'll become extremely frustrated sexually, and that's when he'll start the screaming, nipping, biting, etc.
And from what you have described he's already quite sexually frustrated, that's why he's starting to bite you the way that he is. So the way that you've handled this situation so-far has not been the proper way to do it, and you need to immediately change-up the way you are reacting to his hormonal behavior, because he's only going to get more and more frustrated with you, and this can actually really cause issues in your relationship with him if it goes on and on for a long time. So no worries, it's not a big deal, and that's exactly how you need to start treating it, like it's not a big deal.
***YOU NEVER EVER WANT TO "ACT LIKE YOU LIKE IT", just to answer your question. That's exactly the kind of behavior that will keep him doing it and make him more and more frustrated, and eventually he'll be so frustrated with you that he's going to start attacking you and biting you badly. So never, ever, ever act like you "like" what he's doing, nor do you want to ever "praise" him when he either regurgitates for you or he starts trying to mate with you. And again, you also don't want to "punish" him or "scold" him either...So how do you handle this situation then, if you aren't supposed to act like you like it or praise him for doing it, but you also can't scold or yell at him, or punish him for it?
The answer is very simple: You do absolutely nothing, you show no reaction at all. You simply STOP THE BEHAVIOR and remove yourself from the situation immediately. Then you give him 5-10 minutes to cool-down by himself. That's it. It's very simple actually. FOR EXAMPLE: Any time that your bird starts trying to either #1 Regurgitate for you/Feed you, or #2) mate with your hand, neck, or any other part of you, you simply need to either have him step-up onto your finger/hand or if he won't do that then you need to just get a hold of him and either put him right down on the floor, or take him to his cage, a play-stand, etc., and then walk away/leave the room that he's in for 5-10 minutes so that he can cool-off. Now you don't want to shut him inside of his cage, because he might look at that as a "timeout" or a punishment, and you don't want that. All you want to do is simply put him down somewhere safe and then walk away and get out of his sight for 5-10 minutes. If he is flighted and is able to follow you out of the room, then be sure that you put him in a room that has a door you can shut, because again, you don't want to shut him inside of his cage like he's being punished...Also, a lot of people tell their birds "NO!" first and then put them down, that's your call and it's not a bad idea, but it's extremely important that you are careful about the tone-of-voice that you use, because you don't want to yell, scream, or scold him. So you can say something like "No, we don't do that." and then directly put him down and walk away, and use a firm but nice tone-of-voice. And after the 5-10 minute cool-down period you can go back to the room and then just act like nothing ever happened, and carry-on normally. If he does it again, then again you nicely say "No, we don't do that." and again put him down and walk away from him for 5-10 minutes. That's all you have to do.
Luckily your bird is a Green Cheek, and this method usually works extremely well on them because they are definitely "Velcro-Birds" who love attention and affection, and absolutely HATE being ignored or "shunned"...So usually after doing this a few times, they get it and it then starts to taper-off. But it's extremely important that you follow the exact same routine every single time he displays the hormonal behavior, and that you execute the plan immediately the second he's on you and you see him start to Regurgitate, or the second you see him starting to try to mate with you.
****Let me stress something else to you that is very important. You don't want to do this to him UNLESS HE IS ON YOU/WITH YOU, AND UNLESS HE IS DOING IT TO YOU! If you ever see him trying to mate or actually is masturbating on something other than a person, like a toy, a perch, his cage bars, his play-stand or play-gym, a food dish, anything other than you or another person, then you should just ignore him and let him do his thing. Only use the corrective-behavior technique when he's exhibiting hormonal behavior with/on a person. That's it.
***And just in-case you don't realize what the start of hormonal behaviors actually consist of, as you've talked about him "trying to feed you", so I'm assuming you're saying that he starts Regurgitating for you...You want to immediately say the "No, we don't do that" to him and put him down the second he is on you/with you and you see him starting to either Regurgitate for you, or you see him starting to try to mate with your hand. I don't know if you've seen him do this before, but usually this starts with them clenching both of their wings close to their body but hanging them both lower than normal, and they typically start walking around your hand, foot, whatever part of you they are attempting to mate with, in a frantic fashion with their wings held close and hanging lower than normal, and while they are frantically walking around your hand, foot, etc. like this, they typically are making quiet little "chirping" noises that aren't noises that you hear him make normally. It's a very distinct behavior, you'll recognize what it is as soon as you see it. Also, he may just clench his wings to his body and hang them low, and then climb right up onto your hand while making those little, quiet chirping noises, and immediately start rubbing his vent on your hand. Sometimes they just start it that way, and sometimes they try to actually grab your finger in their beak in order to move it into a certain position for themselves, lol. Either way, the second you see him doing any of these behaviors, just execute the routine, and in a short amount of time he'll understand that this isn't something that is ever going to happen...
As for the current biting that he's been doing, it should start to slowly stop all together after he starts to understand that this isn't something that is ever going to happen. How you handle the biting is up to you, but again, the "Shunning" technique usually works extremely well with Green Cheeks because they love attention so much that the minute you take it away they when they're doing something they shouldn't be, they get the picture very quickly....Now with the biting you want to handle it a bit differently, as the biting IS A BAD THING, AND DOES REQUIRE PUNISHMENT OF A SORT. So whenever he bites you (make sure it's an actual, purposeful bite and not him using his beak to climb up onto your hand, etc.), you need to firmly and loudly say something like "NO BITES!", and then you immediately put him down on the floor (they hate being on the floor, as they are the lowest thing in the room, especially if he's clipped, if he's flighted then he'll most-likely fly up to his cage or some other spot, which is fine as long as you don't react to him in ANY WAY AT ALL after you put him down). So you say "NO BITES!", put him down on the floor immediately, and then immediately turn your back to him and totally ignore him in every way for about 5 minutes. Any longer than 5 minutes and he'll lose the "why" of the whole thing. So when he starts crying or screaming for you, completely ignore him. Don't make eye contact with him, don't acknowledge his existence at all. It's better if you don't actually leave the room, as that kind of takes-away the "shunning" part of the whole thing; you want to have your back turned to him for a full 5 minutes, and hopefully he does start to cry and scream so that you can keep your back turned to him and completely ignore anything that he does. This works very well with Green Cheeks...
