@sagiii
They are both difficult decisions/questions for sure. I feel like only further prototyping would give you conclusive resulst here. I will gladly give you my opinion on those two topics however.
- When I play your game the slow mo mechanic of it gives me some "Superhot" vibes. And imagening Superhot without unlimited slowmo would probably not work (or you know... time moving when you do). If slowmo were to be limited the gameplay loop probably needs changing as well. You probably would not be able to play with the "limited bullets" aspect as much. You could then instead work with weapon pickup mechanics as seen in Hotline Miami for example (emptying your current gun, throwing it at the next enemy and then picking up another that isnt empty)... but that is just off the top of my head and would need lots of experimenting. So with unlimited slowmo you could explore the "puzzle" aspect further with it being limited the "action" aspect.
- Forcing the player to move by simply scoring him worse is something that can work (again hotline miami) but can also feel very forced and to the detriment of the experience. In hotline it is for example very much supported by the rest of the gamplay and music. Camping could be reduced by for example making the bullet drop to the floor if it hits an enemy. Or something else that gives you good reason to leave your spot.
I bet if you think about this some more and especially prototype a few possible mechanics you will get there.