I'd scrape with a one-sided razor blade. Find blades at any hardware store.

Try some denatured alcohol. Get a stiff putty knife and wrap a thin cotton rag soaked with the alcohol around it in order to get some leverage on the paint you are trying to remove. The alcohol works best when you saturate the paint so it will work better after a minute or so than it will initially.

why did you start a new thread? check your other one.

I only see three cables in that box, so I'm a bit confused about the reference to four. Anything is possible. You really should have investigated this before removing the switches. As it is you'll have to trace out things rather than making assumptions. I do note a couple of issues (other than the crappy drywall work). The box looks to be set too far back to be legal. The box needs to not be set back within a 1/4" of the finished surface. Another clue is the presence of black tape on the white wire leads me to believe that this may be a switch loop (or some other circuit buggery) and not a feed from the panel or a direct line to the light or heater. Again, you'll need to check the wiring at the light/heater end. The cable clamp for the left side/bottom cables appears to be missing (you need to put it back when you are done). Further, if this circuit serves other rooms, you may NOT put a bathroom receptacle on it. A further note, remember all bathroom 120V 15/20A receptacles require ground fault protection.