Thanks for playing! Yeah, inverted controls and distortion together are a nightmare haha
The slot machine with 1 item is supposed to let you replace debuffs or "instant use" items like heal that takes up space without any active effect. For example if your items at the moment are Boss Invulnerability, Heal, More Damage, More Ammo and Bouncing Bullets you can spin x1 two times to replace the first 2 items, and potentially have 5 good buffs. It's also the only way to get new weapons, like uzi, shotgun and bazooka (they are more likely to appear if you're using the default pistol ate the moment), and as you can stack ammo and damage items it's possible to kill the boss really fast with the right combination
I think that I'll add some tips in the game's description