Thanks for playing! Funnily enough with the shield thing - there IS in fact a mechanic where the Sal Skirmishers (the shield enemies) DO in fact take more damage from the sides and rear (and less from the front) it's just that because of financial constraints the sprites that show this have yet to be made/finished so it doesn't really show very well. But yes - it is (sort of) present.
Your comments on the pistol have given me the idea of the pistol being a weapon that gets gradually upgraded over the course of the game. Could be an interesting mechanic.
I don't know if I'd say the rifle is *worse*. The idea is that the pistol is supposed to be powerful, but unreliable if you end up missing or there are more enemies. The rifle and shotgun would thus be more consistent overall.
The big doors DO sort of have a tell for if there's something behind them - whether or not they have any text. But yeah I get that's way too subtle. Will probably end up adding bits to them soon.
The switching weapons thing is actually intentional. There's a small delay before you're allowed to switch weapons to keep players from juggling guns - and thus make the choice more of a commitment.
The pistol disappearing during reload is a known thing, yeah - the animations aren't done yet unfortunately.
The guardrail pixel infuriates me as well but unfortunately I'm not sure how to get rid of it since I don't know what's actually causing it.