This is very well laid out. I tried it out and met my first enemy: a Bugbear. We engaged in combat and I rolled, hit, and did a little damage, then he rolled and missed, then I rolled, hit, and did a little damage, then he rolled and missed, and so on. He never managed to land a single hit on me, and after doing so many rolls where it felt like I was just slowly whittling down a number, I had to put the game away.
I'm not sure if it's possible to speed up combat somehow by making monsters stronger but with less health? Alternatively, you could make it so that in every round someone receives damage so there aren't a bunch of combat rounds where nothing happens. Either way, this is a cool little project you've got and I wish you the best in the future development of your game. With a bit of fine tuning, I'm sure it could turn into something pretty awesome.