Stage 1 & 2 mons have 3 hp. Stage 3 and onwards will begin to add dice and the touhgness modifier to their hp.
e.g. Mushmon: 3hp +3d3 (1,1,2) + Toughness (+1) = 8HP intotal.
The amount of dice you use is based on the mon's stage (so stage 3 will use 3 and onwards), if the mon evolved just add 1+3 and the toughness modifer from their previous stats (so if a navimon evolved into a roamon, you use navimon's stats, not roamon's this is the base rule from the system and it took an embrassingly long time to figure that out.). Humans are at the same level of Stage 3 mons so you just do 3 + 3d3 + toughness.
We milestoning this, yes I'm do use the exel sheet to get the stat blocks for digimon but I'm tracking shit on paper and don't want to burn myself out, and the evolution is set as well to some degree.
I'll flip flop on the skills here and there, like just using the skill that is described to only inflict a status condiction but instead it just deals damagae in this story. Rule of cool or more better, whatever fits that situation at the time I write it. Now for damage, it's based on what type of skill it is. If it's the main skill then it does the mon's stage worth of 3ds and secondary skills are just one less dice of the mon's stage. Basic attacks that aren't attacks like punching, kicking will just be a single 1d3 + power modifier, this is mostly so that the human can do shit if they want to attack.
This is mostly for partnered mons and humans. They share a turn but thanks to the fact that there's two (or more, up to you) in the group they will have two actions in that turn, so you could have a human-human turn or a mon-mon turn or mon-human turn and human-mon turn, up to you. Bosses will also hace multiple turns just to make it more fair for them along and adding extra digimon to normal fight as well for fairness.
They will be treated as Digimon, I'll put the fan-made stats somewhere and just think of the card game for evolution wise. Both can evolve into each other and app-fusion is the same as Jogress evolution, up to you on if you want it to permament or not.