My dog is touched in the head..?

PLEASE READ WHOLE STORY: I think my 3yr old Chihuahua is retarded. He was given to me from a relative when he was 1 1/2, I regret that day. He is a HUGE pain. He jumps on my couch constantly, he pees/poops whenever or where ever. He is forever trying to lick my other dogs' butt. And is always searching for my other dogs' pee & when he finds some and licks it, and makes this chattering face that ercks me so much that I wanna punch him. I dont want him around my child on the way. My friends told me to get him neutered and it was a waste of money -__-. I took him to my other dogs' trainer and he bit him. My other Chihuahua than I personally bought for $1500 is my ideal dog, is perfect. I tried and tried to give him the same training and life as my other Chihuahua he is just, slower. I'm just tired of him and failed efforts. Should I give him to a shelter so they can try or what? Can someone PLEASE give a reasonable answer, thanks.