I understand mental disorders because I have a few diagnosis myself, but my husband is concerning me.
First, he displays some serious Munchhausen behavior. Now there are even nurses coming to our house, but typical of him, he doesn't follow orders so he will get better. Also he sabotaged two colonoscopies by eating when he shouldn't and there is actually a problem to look at and now they won't do the test again!

The first test, I thought I made a mistake that messed up the test and he didn't correct that, the nurse had to tell me later he did it. And he tried to sever fingers! He's already missing a finger because he lost it to and infection they say he gave himself! If he has a medical problem, he tries to make it worse.
Second, he recognizes that I have low empathy but now he tells me he does too. I didn't realize this, but it makes sense based on how he behaves.
I know he is diagnosed with Personality Disorder NOS, and other things, but I don't know if there is the possibility of saving him, or maybe I should just leave.

You have not caused his mental illness.
You cannot 'save' him or 'fix' him.