Here is the info on tire markings, including load index:
https://www.tirerack.com/tires/tiretech/techpage.jsp?techid=35
Load index of 95 corresponds to a designed load rating of 1,521 lbs per corner, or 6,084 lbs in total.
That's about 50% above Model 3's weight.
TM3 LR weights 3,805 lb, so technically, anything above load index of 79 (or 81 for AWD/P cars) is perfectly safe.
Tesla Model 3 - Wikipedia
Since you can not even buy a Michelin tire (S4, MXX4, etc) in 18+" sizes with a load rating below 84, load rating # is basically a non-issue.
For all practical purposes, any tire of the stock diameter will always have a load rating well above the minimum for your Model 3. I can't even recall the last time I bothered looking at load ratings when shopping for tires.
Your 225/45-18 size is going to be only -0.25" lower than stock, with -1.9% lower speedometer reading. All perfectly fine.
Go for it!
a