hes probably getting this way because he resents he help your trying to provide,
I wouldnt change much of what you are doing.
Refusing to drive him to bars is the right thing to do.
But maybe stop offering to help him with his diet etc.
Stop asking him to come over for a month.
Find something he would enjoy and call him up and say hey im going to ...... And ask if he wants to come.
Talk to a counsellor for yourself or an organisation that helps the families of those with mental health problems.
Call him
Just to say you love him.
But not too often. Ask how his day has been and just listen.

Goodluck
Xxxx