This is a horrible situation to be in. I was in a similar situation, except in my case the Xs disability was primarily, but not exclusively, psychiatric. I can tell you that I hung on out of guilt and pity and I probably even got married in the first place out of guilt and pity and the desire to "help someone in need". I can also tell you this for sure.
It doesn't work.
In time, your pity will turn to resentment. It might even turn into anger. It will lead to your own deterioration and self-destruction. And I'm going to tell you something right here and now that might make every person on this forum hate my guts and I don't care.
Get out. Get out and save yourself while you still can.
You might find out what a cold-hearted [censored] you can become once the cloud of the relationship has been lifted. I know it surprises me how very little I actually care about what happens to my X. I believe she will ultimately become one of the "bag-ladies" with $350K in the bank (my retirement savings). I hung on FOUR YEARS TOO LONG. Four WASTED YEARS.