Really cool but I noticed a few things.
1. He jumps like REALLY high, I don't really see any reason as to why that is, I doubt its for progression as you have rocket jumping and you can toggle running, but this makes it insanely awkward for match play. Maybe just a cvar to disable jumping would help? That or maybe replacing it with double jump idfk.
2. Infinite height explosives. Why? I understand that THINGS in the original doom had infinite height with their height values only being for map collision, but that isn't exhibited here, infinite height explosions were only a thing as a by product of infinite height. I think all multiplayer source ports have this disabled by default. Not much of an issue because most of the time in match you'll only be firing rockets at a mid texture, but still something worth noting.
3. Was originally gonna mention the lack of auto aim on the bfg tracers, but to be fair it would be a bit op with freeaim bfg, and also the fact that srb2 has no true hitscan which would make it hard to implement. However the ability to disable enemy drops would be useful for maps like sonic doom 2.
4. Ok this is like REALLY nitpicky but if you're trying to stay perfectly accurate than the super shotgun shouldnt light up the 3rd weapon indicator on the hud, since only the normal shotgun does in the original. Also on the topic of the super shotgun, the super shotgun correctly (or incorrectly I guess?) has a 7 frame muzzle flash compared to the original doom 2's 9 frame muzzle flash (although thats like REALLY fuckin nitpicky.)
To be more positive though, this mod is like really damn good. Sticks very close to the source material, has all the power ups and stuff with ACTUAL weapon progression unlike some other similar mods *cough* *cough* tails guy *cough* *cough*, has a full screen hud (which seems to be a weird mix between the old zdoom 1.2 hud, boom/eternity hud with the weapon indicators and such.) Also splitscreen support is cool, I think the coolest thing though is the fact that, looking at the code, there seems to be support for custom weapons and items. Thank you for that, you are a real one.
As for some of the issues you mentioned:
1.- The Item Drop system not being balanced is kind of a intencional, as there is 0 way to actually determine what kind of progress you are in campaing, singleplayer or co-op. A weak solution may be add randomized chances instead of literally all random.
2.- The BFG has tracers, the major problem is that SRB2 lacks any type of hitscan function since it got removed many years ago. So everything like the Pistol, Fist, Shotgun, Chaingun. Is just a hacked fast missile with Rail Ring's logic from SRB2's Ringslinger and there is no way to re-implement that other that STJr re-adding those functions.
3.- The Chaingun fire 2 bullets even with tapping the fire key once, the entire development of DoomGuy was based using the Doom's source code while finding a way to implement it into SRB2 itself.
4.- The HUD is different yes, but it's because things like keys display are worthless to implement as SRB2 removed that system already. As for the blinking, because it looks as a neat detail. That's all.
5.- About enemies waking up on firing, it's totally not ideal. Already talked about that with my playtesters, even if just a flood fill function to wake up enemies, going through all the map is just bad in performance as SRB2's maps are a lot bigger than Doom's map. And waking enemies is totally worthless too since enemies in SRB2 doesn't travel the map in long distances since it's practically impossible for them.
6.- And about looking up and/or down, Autoaim depends of thesse same hitscan functions that no longer exists. Simple.
After all, my goal for DoomGuy is just to have fun. Not to be critically 100% accurate, since already tried to do the most things possible with the limits of SRB2's engine.