Maybe stick with 7.5"?
Honestly man, you seem to be really overthinking this!
If you can find a good 7.5" wheel, then then go with the 235 section tire. But honestly I would just stick to 7" and 225. You have nothing to gain from the extra centimeter in width, unless you push the car hard enough around turns to want more cornering traction, or your engine is tuned, for example.
My Mazda 6 comes stock with 7.5" wheels and 225 section rubber. Wider than 225 is not necessary for the stock 2.5.