Abnormal Psych in Movie "As Good as It Gets"

In the movie “As Good As It Gets” Melvin Udall, the main character, has OCD which is obsessive compulsive disorder. He washes his hands with a different bar of soap five times. When he opens his medicine cabinet in his bathroom it is full with bars of soap. Melvin will not step on cracks when he is walking in public or around his house. He has carpet flooring in his apartment. He uses plastic gloves to touch any doors or anything he could get contaminated by. Melvin never says why he is the way he is. He is very rude to people that get in his way or just talk to him.
He puts his neighbor’s dog down the garbage shoot because he peed on the floor in the hallway. Melvin was confronted by the dog’s owner, Simon, which is his neighbor. Melvin told Simon he did not know where his dog was. Simon walked in on his house getting robbed and he was sent to the hospital. No one in the apartment complex wanted to dog sit for Simon, so the last person to take him was Melvin. Melvin did not want the dog because no one has been in his apartment before, let alone a dog. Melvin would pick the dog up with plastic gloves and petted him with the gloves on too. Melvin has to go somewhere in town so he brings the dog with him and he realizes that the dog does not step on cracks either. This made Melvin like the dog a lot after he found this out.
Simon later gets out of the hospital and Melvin acts like he does not want to give the dog back. He gives the dog back knowing that that is the right thing to do. Simon brings him home and all Verdel, the dog, does is sits by the door whimpering. Simon is more devastated by his dog wanting to go to his mean neighbor instead of him. Melvin comes over and tells Simon that the trick is he keeps bacon in his pocket. Melvin takes the bacon out of his pocket and gives it to Simon. The dog ignores Simon with the treat and goes to Melvin. A couple of days later Simon yells at Verdell that if he wants a mean owner then he would yell all the time and be...