Thank for the update! I recently played with my two sons and they love it. I honestly played based on your youtube video and didn't realize you had already written 3p-4p rules. But to accommodate the three of us, I just replaced the second "4" card with a third starting card. This made the games play much quicker obviously but they had a lot of fun.
I was planning to add a fourth player by extending the grid to 5x5 and including all "4"s , three "5"s and one "6" card (I like the idea of having one large number card that's bigger than the grid size). I have no idea how that will feel. I'm excited to see what you come up with. And if there is a physical edition I'm excited to support that as well.