I also have put this in the steam forum, but it will likely not be approved since i dont own it on steam.
On hard i dont think its possible to beat him, since he keeps spawning shooting spiders, which already are tanky on there own. I get that you use them to resupply to player but they already take a lot of resources to beat and there attacks are pretty strong. I also found it he spawns them after you spend a few minutes in the fight, my suggestion is to spawn them when he hit half health or every 25% and have them drop big ammo packs for just the pistol/smg and the shotgun/ssg and one spider to atleast drop a large medkit. I hope you guys check this forum.