I think your pretty spot on with those laws.......I'm running 15x8/15x7.5 and havent had any troubles as of yet. It also depends on cops in your area, how you drive, attitude etc.
195/50-15 should be fine all round. Anywhere from 80-140 a tyre depending on what your looking for. Shouldn't have too many issues with stock height/wheels, but depending on how low you go you need to either roll or flatten the inner edge of your guards as you will definately get scrape.