First of all, very charming concept and feels extremely fun and unique, was surprised to realize you made this on your own! As for difficulty, I think I had trouble understanding it in the very beginning (a lot of text in the tutorial but also a lot of different stats to understand). I think it might help to introduce all the concept a little slower. So instead of the text, it might be nice to every combat or encounter introduce a different part or have one combat were you handhold the player.
As for balance, I was going to suggest making it less difficult, but when I really got the hang of the poker scores it was definitely way more doable, I simply think the game has a bit of a learning curve.
Quick bug notes, any mutagens you buy do transfer when you start a new game you do keep, not gamebreaking but not sure if it was intended. Also, and I ran into this sometimes, I was not able to score the cards (either it would say it is an invalid hand when it is not or I would simply not let me score at all, locking me into combat (see screenshots below). Saw in the rating comments someone else had the same problem, hope you can still find and fix that bug!
Long story short, amazing game, had a lot of fun playing!