If you are on a tight budget, don't spend money you don't need to.
That oil gauge from Cycle One Off is not a necessity by any stretch of the imagination. If you are worried about the "dreaded orange o-ring" take a look at it when you replace your oil sump in the future. It will be easy to see. Sean Morley sells a "oval o-ring" mod that can be done if you're really worried. Cheap and easy if you already have the oil pan off. You can wire tie the oil tubing up if you're really concerned or, buy an engine saver bracket. Just my opinion, but none of this is really necessary. Just warm the engine up to temp before hammering on it.
I'd not replace those coils as Sean and Kyle both mentioned.
If you want to replace the plug wires, you don't need special tools. The spark plug boots screw right into the wires. Since you've taken off the coils you see they screw right into them as well.
Check the coils for any corrosion where the wire plugs in.
The boots can be taken apart and cleaned up if you feel they need addressed. You can test them per the manual. Dannymax wrote a how to on this years ago.
The stuttering issues you describe sound like a carb adjustment issue to me. The rpms you mention sound like its mainly a needle issue.
If you're not looking for max power the air filter setup you have is fine (stock)
#1, buy a "Y" for your airbox. Check with Sean Morley, Captain Kyle, or Ebay. Since you have aftermarket exhaust, you can ship the Y up to 1/4 with washers to allow a little additional airflow.
You mentioned the bike has a carb kit. Its definitely not stage 7 so, probably stage 1 which folks typically have issues getting to run correctly.
#2, either try to tune with what you have or, go back to stock jetting. Install the Y first and then test. If the same problem persists you can try to adjust the carbs per the attached document.
Good job on synching the carbs. It make a big difference if things are off.
You should also check the vboost cable for proper adjustment.
https://www.vmaxforum.net/threads/how-to-adjust-vboost-cable.4361/
You can leave airbox on, remove the chrome H-covers from the side of the carbs, loosen the set screw, cycle ignition, then tighten set screw. This should remove all slack from the cable.