Back space has nothing to do with rim size width in respect to inside fit. Excepting things like calipers. So a 15x8 and 15x10 rim with both at 4" back space have the same inside clear. That extra 2 inches is on the OUT side. so you added 4"inches of width as compared to say a 35x12.5 to your Jeep add the 3 inches of back spacing. so your 7"wider now. Thats more width than most go in hieght.
Why are going 14.5 wide, unless you are running say 40"s. But 36? very hard on the axles bearings C"s ball joints stearing the list grows. MPG is out the door with 14.5 wide. odd choice for sure.
I run 15" on my Jk with 35"s. Steel though. as hard as i am on the rim seem a total waist to put an money in rims