The thing is, I have carried the financial responsibility for everything.
which means, even with the BEST of intentions, you've helped finance his addiction. which is not YOUR fault....that's a thing that some addicts do....find someone to "take care" of them, poor helpless them. they act so inept, so unsure, so.....god.....NEEDY. and we fall for it. our maternal/codependent side rises to the occasion.
and here we are, years later....stuck with as you said, dead weight.
LET HIM GO. he had years to watch you...to learn how to run a household, be responsible, pay bills....basic living skills....yet he choose to stay stupid. much easier than getting off his duff and doing ANYTHING.
make a clean break. let him go follow his path. you follow yours.