Literally laughed out loud at your Chris comment!
I say Chris is a good guy despite playing with Rose's heart because he hasn't cheated physically on Rose. Sure, emotionally he may be unavailable which makes me question why he would even propose to Rose in the first place. He's been nothing but chivalrous and kind, with no sign of ill-intentions. To me his only crime is he just is incapable of loving Rose as much if not more than Ada. Maybe they would have been better off as just friends instead of lovers now engaged to be married.
Playing as the MC, I would pull him aside and tell him Ada still loves and wants to be with him. That it's not too late to be with the real woman he loves and to sweep Ada off her feet and elope with her....
...meanwhile, this leaves Rose for us to be that shoulder to cry on and be her one and only true love who will give her the love and devotion she could never get from Chris.
I may be naïve here for thinking about trusting Rose and giving her my heart, but as a hopeless romantic, I choose to believe Rose's indiscretion was borne out of her desperation being with the wrong man, in a hopeless situation with no one willing to help her figure things out. Once she is paired together with her true soul-mate, there will never be a need to worry or fear from future infidelity from the MC or Rose. In fact, the best news possible would be an ending where Rose finds out she's pregnant with the MC's baby and in their happiness they elope/get married and are excited at the prospect of starting their family. The MC vows to be the kind of loving father his own distant father never was.
On a side note, I am genuinely at a loss trying to understand under what justification the MC's mother had for straight up walking out on her family. All we know is it most likely has something to do with a former/current at the time patient, but it would be way to obvious or on the nose to assume she got too close and there was some kind of infidelity. Maybe she had some kind of shady, dark secret of her own she was afraid would be exposed and felt it would better for her heartbroken son to forget her and move on with his life over ANYTHING she may have done in her past like murder/manslaughter. Tragically not only did she destroy her own family, but indirectly caused the implosion of the only other relationship with a woman the MC had at the time, essentially destroying his whole support system, who knows what would have happened if Damon and by extension Danielle weren't around and in the MC's life.