For what it's worth, I think your takeaways are spot-on - I forget if it was in the comments for your May Wolf game or if it was the maze and sliding block puzzle one, but I made a similar comment about making sure the gameplay and narrative are working together so you get a satisfying payoff from moving through each section, and I agree that this was a really fun idea that could've been executed better. But yeah, jams are hard, especially when you're trying to do so much as an army of one, and I totally understand how a lot of what you envisioned couldn't make it to the final product.
Regarding the conflict between Dierre and Lufo, to make the Game Boy premise work, I think the inciting incident is less important than their current attitudes to each other. Like you can still have the conflict start with something mundane, but if they're pissed and bitter towards each other at the start of present events, the arc of the Game Boy section can be them growing to realize that their resentment to each other was dumb and they both need to get over it. Or you could go in a completely different direction, just throwing another idea out there for additional perspective.
Ultimately I think it'd be cool to see you stretch some of your ideas out into projects that aren't limited by jam timelines so the narrative and gameplay both have enough time in the oven, but yeah definitely keep it up, you're only going to get better and better from here.