I don't know, honey, I'm not seeing your "red flags". I am just going to have to point down to what Aldi's already said below, because I think she's already talked about the buttons he knows how to push (and it's not bad to push buttons, unless you what you're looking for is a completely nice, safe, and sterile relationship -- buttons are a big part of how people grow in a relationship).
the only reason Show has given us for Marc wanting Roman to come out was because MARC didn't want to hide/live a lie. That actually is not true. What was said was that they broke up because Roman wasn't ready to come out, and Marc couldn't live a lie anymore. It's not the same thing at all -- there could have been 12,328,028 other reasons that he wanted him to come out, and 12,328, 027 weren't to do with Marc wanting to hide. That's only why he couldn't take it in the end.
As for knowing where Roman is, I hope you're then okay with saying that Roman stalked Deniz all through the first 70 episodes, because he was showing up and catching him in the locker room all the time too. And really, when you're interested in someone, you don't try to be where you know they'll be? Please. (Or maybe I just have stalkerish tendencies myself.) As for the dream ice show thing, what do you mean? Just appealing to his dream? Is something wrong with that? (Please don't tell me you're one of the Ice Show deniers, I don't know if I could take that.) The quips I think are something he's bitter about, little digs. They make me pity him more than anything, that he still feels cut by that. And as for emasculating Deniz? But darling, it's ever so much fun.
Really, am I just a horrible person, or are these not things that you would do too if you were interested in someone? Or are you all nice and sweet and completely above board?
Bottom line, I'm not getting an obsessive vibe from him at all. If Roman could, just once, give him a definitive no, I think he'd be gone. I wonder if you're not displacing some of your negative feelings about Roman and his indecisiveness onto Marc. It seems hard to believe in any way that he's betraying Deniz, and it's so much easier to offload that resentment to Marc. But I think it's pretty unfounded. Especially when you are shifting the blame from Roman's mixed signals to Marc's shoulders. Not buying it, soz.