Cool mechanics for a TTRPG! My friend and I are really into these kinds of games, and have actually been toying with the idea of playing a card-based version, then you come along with just that. We enjoyed the way rounds work and the way limb damage works.
Unfortunately, we were only able to run an encounter with 2 people, one as GM and one as PC. This may have been a mistake because the PC got absolutely demolished by the Dreadwolf. Playing with 2 people also made it hard to play cooperatively for obvious reasons, so we needed another player to fully test that aspect of things. I know TTRPGs typically require GMs, but I wonder if there's a way to automate the monster's actions by randomly drawing from their deck. Cards are a really useful tool for that kind of thing.
Another problem came up with how we were using Interrupts. It seemed like the PC was constantly being interrupted by the monster's actions. There's something really cool about being able to see the timeline and make decisions based on that, but I could see getting into situations where either the PC or the monster is constantly getting interrupted if they take actions that cost more than 0 time.
I like that you included skill checks, but they were a little confusing. What number was I meant to judge the player's success against?
Overall, you have a cool foundation here. I could easily see this being turned into a cooperative board game like Gloomhaven with some automation and some tweaking, but it could just as easily be a full TTRPG with some elaboration (which it sounds like you are working on).
Can't wait to see the finished game!