Leeny,
"What I am afraid of is that I'm going to be penalized for divorcing him--made to support him"
What? You aren't supporting him now? Even if the state rules you have to pay spousal support to the YUTZ, it will be less than you are paying now to feed, clothe, shelter, and entertain this waste of breath. Additionally he is costing you your health. Spousal support is intended to allow the partner with lesser economic means to live the lifestyle to which they have become accustomed. With his entitled benefits, he will most likely be in better shape than he is with you negating support. What does he need to maintain his lifestyle? A couch, a cot, a TV, some TV dinners?...I doubt you are on a diet of filet mingon and caviar with silk sheets and a 65 inch home theater with Clipsahorn speakers. Don't sweat the spousal support just produce your income statements.
"targeted with disapproval for deserting a disabled person."
Anyone who disapproves is not worth your time. These idiots are as sick in their own ways as he is.
"I'm imagining the divorce action to be like a criminal trial where I'm going to be the one on trial."
Nope! this is civil. Divorces get nasty when you are proving wrong doing, there are children to support, or lots of money. A case of the spouse accused of abusive behavior or adultery getting no support or settlement of the property for impropriety in the marriage for example.
"He's told me several times that his mother knows in heaven what is happening on earth and is upset with me about what I'm doing."
Whenever H opens is mouth with one of these patent lies, call him out. Say, "You are a liar (or other appropriate description)." Or "That is not what your ___(relative) says."
Anything he claims for himself, say, "No, I paid for it. It belongs to me. (you could even claim his undies, but I don't think I would other than to point out your generosity in letting him have some)".