Hi there,
I think there is patience and there is patience. Some cats are talkative and some are not. You don't know the history sadly, so it may be the cat was abadoned or left and he is so used to calling out.
Either way if feliway does not help, then maybe this is not the cat for you. Some cats don't suit everyone and as said before, its no reflection on you as an owner.
Devoicing. I know this was an off the cuff remark......you can tell very much that you care for your cat, otherwise you would not have bothered to try different things.
You will get there, I know how difficult it is when they wake you at silly hours and sleep deprivation is the worst of all tortures. Ear plugs aside, try feliway and maybe a cat specialist.
Good luck, but don't feel bad if you have tried everything and it still doesn't work. ...Maybe this cat needs to be in an environment with other animals or access to outside when he gets the confidence. At least you were willing to try.