What makes you think Steam is going to be any better? It could be a potential new revenue source, but he can't follow the AWAM format on Steam, with their restrictions. He would have to use something close to DoL, and even then, he would have to remove any copyrighted material (symbols, songs, etc.) used in that format.
Right now, he has to create two different versions of the game, so he is doing double or triple the work right now.
Dylan becoming a 2nd MC fits into the story narrative that Sophia's goal at the start was for Dylan to find a GF. How the 2nd MC fits is if Dylan stays with Sophia, then Sophia is the MC as the relationship is building between them. Still, if Dylan is to stray from Sophia, you can't have Sophia as the MC because it wouldn't work, except Sophia would accomplish her goal for Dylan to find a GF. Dylan would need to be the MC for the POV to make it work with Ellie, Christine, Marie, Emma, etc...
If L&P didn't branch out the paths as he did and focus on Sophia only, then you wouldn't need a 2nd MC.