Okay, it seems to me (having read the majority of it) that the ending should solve two issues. (1) Charlie and his self-esteem issue. (2) The one fault that I see in this story (and it's so intriguing that I didn't realize this until now) is that Will needs an issue. That only Charlie can solve for him. Perhaps expand on the "daddy" thing. Keep the kink but put the kink in context so that it's both pervy and healing? The ending is the recognition on some level that these characters mesh and can move forward in all their imperfect selves. Once you reach that point, then there's nothing left to say. It seems to be that throughout the entire novel (at this point) that Charlie is constantly fighting the relationship on some level. Whether his self-esteem is so in the toilet or he has issues with his gay, I don't know, but it needs to be dealt with. Will? Not sure. Perhaps his escape into movies? Something can be pleasure and a problem. Maybe he and Charlie need to have a knockdown drag out fight how all of Will's refernces are to something celluoid. That he's rarely on this earth. None of these things needs to be RESOLVED you understand, but they need to be out there, and we, as the reader, need to understand on some level why they work together. What do they offer each other so that the puzzle piece fits? That Charlie has faith that Will lusts and loves him, and Will has faith that Charlie ???????????

That's what you're working toward.