If you are going all in with a 3.5 inch lift get rid of those 18" wheels and get some 17 x 8.5 or 9. The biggest tires that can fit on stock wheels without wheel spacers really isn't that much bigger than stock. Backspacing is the problem.
with 17s you will have a ton more tire options.
Wheel spacers imho are bad. Many shops won't even work on a vehicle with them on and I doubt your insurance will cover you if one fails.
Like
@BLACKJKU said, you need to figure out your gear ratio. It could be 3.21 or 3.73.. I don't think the rubicon 4.10 was available as an option for saharas, but I could be wrong.
If it is 3.21 biggest is probably 33" unless you regear. You may get away with 35" on 3.73 and are just driving around town.
Don't spend any money until you have a plan. All of the stuff you want to do starts you down a rabbit hole where the jeep will drive like crap if you go only half way.