Hello again friend, I always appreciate you taking your time to do this. Answering some of your thoughts:
There is a new version of the jolly purple horned lads that you can encounter later, basically the same thing but stronger.
I see you struggling with the awful gun tooltips, for example the one for frags do not even list the released projectiles so not very easy to know how strong they are... But I am currently working on improving them and I think its going well.
The different heals have gotten a bit confusing know that there are several, the ones in the shop are actually a lesser one that heals for less and it differs how many there are you can buy. The Ration one is a bit less than the one you can get in the Interstice as you can take it with you. I'll put in exactly how much each one heals, hadn't really thought about there coming up situations where you can choose between multiple ones for example.
Mass isn't really explained anywhere, but its just physics. So increasing your mass will slow you down a bit but also make you more resistant to being pushed around by enemies.
And then onto the slowdowns, I looked into it and apparently its a rendering issue. Most likely because of an inefficient shader I haven't bothered to improve. I don't notice anything at all on my dev machine, so its great you found it.
I think I have it sorted out, if you would like to do me a favor and help me even more here is a test version where Logan starts with a Sawed Off with twice the regular projectiles. If you clear the first level you can hold down the button by the portal and see if its still bad: https://file.io/XLkd3bnt0xeJ
Either way, thanks a lot for your time.