I think that given what this guy has put you through you are justified in not paying anything. It would be different if he had been straight with you, but when he made up the story about the valve job being needed he left the realm of good faith. AND THEN he tells you "it's your problem, come get it." I personally would not allow the car ANYWHERE near the shop in the future so I would not be concerned about the future relationship.
AND you don't know if you're out of the woods yet.
Earlier, I gave you the names of three good shops in the area. I would recommend taking the car to any of them to get the starting problem and the miss straightened out along with an evaluation of the work done.
And finally, how can you not hook up the alternator correctly? It's a freakin' plug-in. Sounds like more of his BS to me.
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe