Eliza it would seem simple wouldn't it. But isn't it always like that, as soon as you get a good thing going, somebody comes and tries to throw a wrench in it.
I can see a little physical similarities between them, but IMHO, SC looks way better than the ex.
As far as not being able to stop thinking about him, girl I've been there and the only thing that helped me was time, cause the more I tried to stop thinking about him, the more I would. Plus I would think to myself, now there's a reason why he's the ex, do I really want to go back there, and then I would focus on the positive people in my life.
Your ex sounds confused, or maybe he isn't because he knows that you're happy and he still wishes that it were him hence all the "we" plans. They can have some nice tricks up their sleeves when they want to. As far as I'm concerned he's playing games with your head and needs to stay in the backseat.
What you have going on with SC seems like the real deal, and it's going to take time to develop and mature. You're not going to get over the ex in one day, maybe not in a week, but you will. I know I wasn't much help, but I do understand.