I also used the hints for the Kitsune-tf (likely easier to find when there is a reason to go exploring after meeting the elf. Maybe have him dispel a force-field in a main-story event as a hint)
and the cat-tf (as I mentioned I didn't really sleep so this would've been hard to find, my fault through)
As you might be able to imagine I explored the map quite thoroughly in my 20+ hours. (I think i spent around 29 hour on the first play-through, more considering the game doesn't count reloads to that time) so I found a lot of the areas easily enough.
Since you mentioned the forest home, I actually went right to it after getting the key. I found the door during the tutorial and figured that'd be the only place to use a key in the forest.
As for the support feature, I didn't use it at all.In my opinion most of the time it is actually a bad idea to use all skills at once.
For example: In human form you have 2 abilities that grant you "dodge all" for 1 turn. Since the system would use both in the first turn you'd waste 1 turn of invincibility. Same for the mouse form where you can delay casting defensive abilities by 1 turn if you use "dodge all" as your first move.
Altogether it just seemed to waste valuable resources (after all 1 turn of invincibility is worth a lot if some of the enemies can one-shot you)
I also remembered one detail that might be a bug:
If I recall correctly Serina reacted differently depending on how you bypassed the puzzles in the first dungeon, however I don't think she commented on rolling the boulders (I did it in human form), instead commenting on the digging ability.
Might just be me having done something wrong through.
Anyway, nice detail.
Whilst starting the game again (to get names right and see what hints I used) I actually found some other stuff:
The description of the "Hand Pistol" is "Effect:"
And whilst the "wooden dagger" has a description bow, axe, spear and sword do not
When exiting the secret shop in the north it displays the area as daytime. Going to another area switches back to the correct time (night time)
I also remembered there is a magic-system for the human form.
I think weakening the inherited skills will have the the positive effect on making it more relevant.
Whilst it doesn't seem to end the turn it easily got overshadowed by the much stronger inherited skills.
If any other questions arise feel free to ask, I'm happy to help in any way I can.
As for me, I'll start figuring out how to break the game some more. (probably later this week)