Anyone else with this problem?

So we've got a Goffin's that we've had for almost 2 years. When we got him he had a nice full set of feathers, though the people who gave him to us said that he had been known to pluck his chest to the point that he would get the skin and bleed. However, he had since grown back all the feathers and seemed fine. We had no issues with him doing anything like this until this past fall (well really, late summer), when we noticed that his tail was slowly thinning out. Then one day he must have plucked a blood feather because he bled quite a bit. We took him to the vet and he had lost a lot of blood so he was very anemic and had to be kept there for several days in an incubator, receiving antibiotics and other meds to help him get better. He was so bad that they didn't even think he'd make it through the night. But long story short(er) he pulled through and regained his health. They did put a collar on him to keep him from being able to reach the tail, because he'd picked it so much that he had a good-sized sore on his hind end and they obviously didn't want him picking at it more. So he had that collar on from Sept to about a week ago, when we'd decided that we should try taking it off and see how he did. His feathers were growing back so we thought he would be pretty good. Well he was good for about 4 days, then he must have pulled out another feather because we saw a few blood drops on the bottom of his cage. It wasn't nearly as much as before, but we were panicking that he'd do it again, so we took him back to the vet. They put the collar back on just this past Thursday and gave us some moisturizing shower spray to use on him, thinking it might relieve itching if that's what was causing him to pick so much.

Is there anything else we can do? We don't want him to have this collar on all the time, but we also don't want him bleeding to death. And I know it sounds bad, but we don't have a lot of money to spend on continuous vet visits. We had a theory that maybe with the furnace being on this winter, he's had dry skin and therefore picks to relieve the itching. Because this really didn't start until it started cooling off. We just don't know what to do. We don't want him hurting himself but it's so sad to see him with that big collar around his neck. The vet didn't offer any other suggestions other than the bath spray.

I'm afraid its probably not itchy dry skin that causes him to self mutilate. I have known several goffins who did this. Your bird sounds like a pretty bad case. If he tolerates the collar (and it sounds like he does) you should leave it on him untill all the feathers have grown back in.
I think your best hope for him to have him sexed and try to find him a mate. If he is a really sweet pet however you should read everything here by Redballoon and his cockatoos (he has videos here too). A lifestyle like the ones his birds lead could be another way to save him, but it is a huge commitment.
There is one treatment that my vet has used with some success on his own umbrella cockatoo. Talk to your vet about Benadryl. I would reccomend you start him on it a week or so before the collar is ready to come off. I say this because he might develope a tolerance to it. I don't know if there is an actual allergy being treated or if it is simply that benadryl makes them a little sleepy. I figure it doesnt matter as long as they stop picking. Of course you need to get the dosage from your vet, don't try just giving him a pill.
Good luck, I'm afraid your going to need it.
Look at the way Redballoon treats his cockatoos and see if you might consider going "cage-free".

I assume you mist frequently, you can add 100% alloe to the mist. you can run a humidifier in the house. You can also add apple cider vinager to his drinking water, I have heard this helps. ACV (apple cider vinegar) has many medicinal uses in humans and animals. One of the woman I talk to does rescue and swears by it like 2 tbs in the water dish. you can also use it to clean you cages it don,t hurt the bird at all. Im sure you also know lots of shredding toys. thats all I can think of off the top of my head. hope you find something that works.

I will address this in full soon