keep the engine stock. regear if you want more oomph.
skip the exhaust. Get an axle back if you want a different sound, or just a muffler. Not worth the money imo
Do you know the service history on the rest of the vehicle fluids? If not, put money and time aside to change all the fluids, especially if you're keeping it for the duration
What "rust protection coating" are you going to use? If you're talking about the body, just wash and wax and you'll be fine, unless you have chipping / other concerning spots.
Basically what I'm saying is forget all the things you have on your list, as they seem like pointless spending. Take the money and get the jeep regeared, a good lift, and good wheels and tires, and you'll be happier