Thanks for the feedback! I already worked on fixing some of those issues like the weapon swapping being buffered and changed the damage upgrade to be only two tiers of actually meaningful change in damage for the next update. I'll also check to see if there's something wrong with the enemy spawns not having their collisions disabled. (though right now standing in the middle when the hole opens damages you, so it might just have been that you would get hit by)
Also the contract doesn't do anything yet so don't worry about not having grinded for it, it's just a placeholder for a planned mechanic.