I'm sorry that this isn't working out for you guys the way you wanted it to, honestly leaving any species of parrot alone for 10 hours a day isn't good for their physical or mental health...So yeah, getting them a "friend" can help, but usually the chances of them liking each other or bonding to each other are slim to none, then you end-up with 2 birds that hate each other and that are alone...In your case the birds bonded together, which leads me to also ask the question of whether or not you got them from the same breeder/place at the same time and they were already together...And if so, they may very well be siblings...If that's the case then they cannot live together in the same cage, and can only be together out of cage under supervision, otherwise you'll end-up with inbred babies...
If they aren't related and they just happened to bond with each other, then that's a good thing for them...However, neither of them will likely bond extremely closely with any people because they prefer to have each other...HOWEVER, that doesn't mean you can't have a happy family and a good relationship with both of them, they just won't be bonded closely with you...
That being said, if and when they start breeding, that presents another issue...They are both apparently territorial about their cages/cage, and that's perfectly normal for all birds...Just allow them to come out on their own and don't reach your hands inside except to feed/water them, and do that when they're both already out...That will solve that problem...It's their "safe space", their territory, and you have to respect that or they will usually become aggressive...But, if and when you allow them to breed, their relationship with you may or may not dissipate, sometimes breeding pairs become very secluded from their people...So that's another reason to not allow them to breed at all...
You did make a commitment to these birds, and "selling one off" like it's a TV or a used car is not the way to go about doing this...In fact, you have no idea what the other bird will end-up being like if you were to re-home it's bonded-mate at this point, as there is no guarantee that the remaining bird would bond closely with either of you, and they could and probably would become severely depressed and this usually leads to Feather-Destructive Disease, Self-Mutilation, and aggression...So the best thing you guys can do is to keep providing a loving, caring home for both birds, allow them to be together, but you may want to consider keeping them in separate cages right next to each other, so they can't breed, and only let them out together under your supervision...Breeding birds is very difficult, trying, frustrating, heartbreaking, and expensive...plus it may just strain what relationship you do have with both birds...So I would suggest keeping them separate when you're not home but right next to each other so they can spend the days together talking and can see each other, and then be out together when you get home, so you don't end-up with a prolific breeding-pair of birds...