will a offset of 35 be ok on my fabia? They are 17" wheels.

Yes, I'm pretty sure the standard wheels are roughly that (although it also depends on wheel width, but you'd have to be fitting some pretty wide wheels for et35's not to fit...)

The standard vRS wheel offset is ET38, so ET35 will only push the wheel out a further 3mm. As Medium says you should be fine unless your new rims are really wide.

only 7.5 or 8j

My wheels are 17" x 7.5J with ET35 and they fit fine with no rubbing what so ever