Awesome work! I think you've reached your design goals very well, the game looks "actually playable" -- both workable rules and offering all the play aides that I would be looking for. I like Strain and Adrenaline, the game seems to have some good momentum. The layout, art and typography are all right-on! Support fire makes sense, modifiers do as well, the charts are clear. I'm really happy about the toy box rules being included, too.
To be blunt, I'd rather use this than Kill Team or Necromunda. I bet it's going to be more digestible than the forthcoming Quake board game too. I also think a potentially interesting game to research would be Frag by Steve Jackson Games. It's also a grid based FPS-deathmatch board game which has done some things well and some thing less so, a good case study. It is also a comparable physical size.
Looking forward to seeing where you take the project! This is probably a big ask, but if you ever take it to Kickstarter, I would be get all over some nice-quality true scale sculpts. I would rather buy some cool gun nuns from an independent creator than get into 40k. Given the game has a strong preference regarding the battle mat used, it could be good to have that up for purchase as well. SJG has used paper, sometimes cardboard hexes, good options on the creator's side.
I hope that isn't too much to put on your plate! Keep up the good work.