He both wants it and doesn't. Yes, he's conflicted. He puts his crusade above love though. That's what matters to him most and that's why he protested and breaks it off eventually. I disagree that he's that much in control though. He said he should have ended it much sooner. So he let his feelings compromise his mission and hurt her, and he regrets it. So that's not being quite as in control as he wants to be to me. He has a passionate side that interferes with his self-control. The romance was unplanned and his feelings ran away with him. He let his pain and anger get the better of him with the mages too. Both very understandable situations, of course. But loss of control nontheless imo.
Fluffy idealism does bite you in the ass in Mass Effect on a few occasions. I think it even gets you killed at one time. Paragon/renegade was a simplistic approach, I agree. But it served its purpose within the story. I too like it when I have to think for a while what to do and not be sure at all. And Mass Effect offers no hard choices. You always know what to do. It's not as straight-forward in DA and I like that.
But... there is no "should." The object is to define your character. Anyway...
About Solas, naturally I don't mean that he's stone, but rather that he can't be said to not be responsible for his actions and decisions. To me it patronizes him and cheapens the relationship to imply that Lavellan is this temptress he can't resist who won't leave him alone. He is deliberative, and he approaches their relationship the same way, asking for time to think.
And, ultimately, I hope/ believe that events will show that it was unwise and unnecessary of him to try to carry his burden alone- a factor of his pride more than actual necessity. He also has been betrayed and needs to learn to trust someone again. The relationship with Lavellan isn't just this stumbling block he let get in his way, and vice versa for her- a Dalish elf leading a mostly human organization that's reshaping southern Thedas. She needs him.