Hi Transformie. I recently went through sleep deprivation and I hated life. It IS torture.
Even my own indoors-only cats wake me up at odd hours, they are crepuscular, most active before morning and around 7-8 pm when insects come out...
Some friends had a cat like that and they just put food outside, let the cat live outside all the time. But that can attract other cats.
Perhaps just put signs and look to rehome it? Or why isn't giving it back to AH an option?
My cats are fixed too and they still want to get out, but they dont meow all the time, the ones howling and meowing like desperate are the unfixed ones.... but I know cats have their own personalities.
When the cat goes to the original owner or new owner you'll feel better. Hope that's soon! And no, you get to choose your friends and romantic interests, good for you for realizing you don't want someone closer than he is. No one is more important than you are.