You just didn't stay with your A long enough - if you had, the sex would have faded. As tend to have... Performance issues... I'm the wrong person to ask about sex with the A since that in my marriage turned into one of the abusive areas. Actually, one of the first moments of sheer joy for me after I left was when I realized he would never be forcing me to have sex against my will again.
As for new dude? Dude, anyone who after two dates is clingy would freak me out, too. He's needy and clingy, that has nothing to do with you. I'd probably tell him I didn't want to see him again, but that's just me. I can't see wasting time with people I don't like anymore.
I notice it's sometimes hard for me, post alcoholic marriage, to know which of my reactions are legit gut feelings about others that I need to listen to, and which are negative self-talk. For example - one guy who was hitting on me post-divorce creeped me out. I never could figure out whether he was really creepy or whether I was just seeing one or two things that reminded me of AXH and extrapolated a future of alcoholism and abuse without really having grounds for it.