FIL lives with us and it's hurting my marriage. Advice?

My FIL moved in with us nearly two years ago. I was reluctant to say yes but it’s the only parent my precious wife has left so I agreed. He's very overweight, depressed (I think), poor, entitled (he thinks people should do everything for him), self-centered, can't seem to tell the full truth even on basic questions (it’s so strange), and his best quality is one of his worst, he's kind (until he has some ignorant opinion on varying subjects) but he won’t SHUT UP. He will ramble on and on and on even if no one is listening.

We had just bought a new first time house and a few months later we moved him in. It was all fine in the beginning, we were working on the house and staying busy so his annoyances were only slightly annoying in the beginning. As time continued and things settled down I started to notice more and more what a disrespectful, worthless (I know, Harsh) slob and pest he is. He would camp out in our living room just talking and talking and talking about nothing and giving his ignorant opinions, and trying to get my wife to cater to him (he knew from the start I wouldn't cater to him). Wouldn't shower, never helped with dishes, awful diet, never took out the trash, would be blaring the TV and music constantly, never did any physical activity. Just a fat blob taking up space. All the while he's just blabbering on about how's he going to get in shape and start walking and eating better, blah blah. I take my word very seriously, so I expected him to actually follow through on some of these ambitions. NOPE.

So probably about 9 months in I told my wife I've had enough, while I'm home he's to stay in his room Monday - Thursday, I can hardly stand to look at him anymore. Oh and I forgot to mention my wife has been pregnant for about 5 of these months already. Anyways, he obeys for a while and makes more and more promises how he's going to do better, blah blah and my wife always believes him. It’s the craziest thing, she will scold him and he will just deflect and tell her how much he loves her.

There's a lot more occurrences and instances than I have space for in this forum but needless to say my wife was scolding him one day trying to get him to clean up his room, which is absolutely disgusting, and is connected to our living room so if the door is open you can smell the odor. And he says something along the lines of "What happened to my beautiful, sweet, compassionate, loving daughter. This is not the woman I raised". I almost LOST IT ON HIM. But I didn't, and told my wife to relay to him that we are not on a speaking basis, I'm done with this a** hole. And when I'm done I'm done. Fast forward about a month later, he keeps trying to have conversations with me and coming out of his room when outside of our designated times, so I absolutely come unglued on him one day. A lot of profanity and I tell him Monday - Saturday when I’m home, you stay in your room and you and me are done. The only thing I want to hear come out of your mouth is "how was your day". Well as you probably know he keeps disrespecting my rules and her rules so every now and again I will snap on him. We tried to get him to move out but it was going to be too expensive with the baby.

Now to the point. I hold true to my word so basically I just don't interact with the guy, almost ever. If he tries to start a conversation I basically ignore him. I could see where this would be hurtful, but that is the point, no one else is holding him accountable, so this is my form of punishment and coping. I loathe this person. My wife will tell him how disrespectful he is to his face, but whenever I address him she sometimes takes up for him even if it’s contradictory to what she said to his face. This has caused some huge fights and its really starting to take a toll on both of us. I just want to be left alone and for him to follow the rules, but she thinks the rules are unfair. I think they are perfectly fair. Any advice on how to better handle the situation?