How short are you trimming his nails? This page has pictures showing how short you should cut. I know you said you tried a cat repellant spray, but have you tried Feliway? It's a cat pheromone spray that can help reduce/eliminate scratching. Like you and others have said, it's a desire for attention, so it may help if you increase the amount of attention you give him and tire him out by playing with him before you cut off his access to the bedroom. I would try your two suggestions (nail caps and a baby gate) too. If you really feel like you need to give him up, I would definitely look into some local organizations that can take him (I can help you find some if you need it) before you surrender him to the humane society. Hope you can solve this issue.