Strange the rears have more dish than the fronts, yet they are the same width? Any pic's?
Tyres 245/35/18 will suit nicely on 9 inch rims. 235's are too narrow and give no rim protection. if your car is 4WD than no need to go any wider than 245's
The +25 offset will be pushing it
I have factory R34 GTR 18x9 +30 and the rears are level with the outside of the guards without the car being too low ie not lots of rear camber.
The wheels you are looking at with +25 offset which will make them sit a further 5mm out than my +30 wheels
At the current ride of my car, near stock, personally I think the rears are on the limit. Once I lower the car it will get better, but will need to check the rear camber is not too much.