To be honest, I kinda flip-flop on whether I feel justified in calling them separate "routes," exactly. To not go too deep into it, it's less that the game has entirely distinct campaigns, and more that your branch approaches the events of the story from a different perspective, highlighting different sides of the characters depending on their mental state. I've been referring to them more as "permutations" in stuff like patch notes because of this.
Regarding the actual branches, currently the major branching point(s) concern the fate of an optional party member, and how that affects the characters and their dynamics going forward. There are three branches in the game at the moment, with some more planned for a bit further down the line, but I want to be careful about how I add more because each branch increases development scope exponentially.
Regarding the MC's role, I can't really say more than I have already in-game, but I thank you for your trust, and I hope I'll be able to deliver something worthwhile.
And on the topic of controls... Yeah, that's one of the bigger annoyances I have with SRPG Studio. It's kinda clunky to play using anything other than pure mouse controls, at least in my experience. I'll try to look into options to make keyboard/controller more viable, but that may just be an inherent engine limitation.