Hello and Welcome! Glad you came out of hiding.
So what to do with Mr. "give me an inch and i'll take the couch"? I suppose you are going to have to restate the lay of the land using short words...you two ARE separated, you HAVE BEEN separated and you only called for some car help. you are not interested in re-engaging and could he please not come over anymore.
there's no way around it, you have to clearly state your wants and needs. and not feel bad for speaking your truth. to back it up you could have the house firmly locked and be out for a sequence of evenings. so that you are not available.
the other recommendation i'd make is a Triple A membership! that way you never have to rely upon anybody else for car trouble. you call 'em, they come out and fix it!