Hi! Thanks for trying this fabulous mess :D
It's a very rough prototype. I had just 8h (before the end of JAM) to work on it, so, well, it looks and works as expected.
You understood the game pretty well. You even got the same ideas as I had ...
Making the humans slower is a simple NPC speed variable change. The point of collecting the potions was indeed to use the blood as your stamina/health. By collecting you should regain your health. You should also have the ability to sacrifice some of your health to dash forward which should be rewarding if you managed to dash on an NPC. Sadly this was out of my time.
On the game page you can see a list of planned features. I will definitely finish it after the game JAM so it is a simple infinite catching/dashing mini game.