1. Loads of choices for where depending on the wheels you settle on - wheelbase, demon tweeks, Amber Performance, etc
2. Stock are 17x7" et48
3. 18's will fit fine
4 & 5. These are just personal choice really, Google ones you like and see if there are pictures fitted to an 86/brz/frs
6. Some places will fit and balance, some won't just depends where you buy from
7. Not really. Just make sure you have the right bolt pattern and centre bore / necessary spigot rings (most places will supply these anyway)
8. Brand will come down to the style you want. Konig are fine.
The wheels you've pictured were mine. They are some of the only ones with a ring on - you'll limit you're choice a lot if that's a must have. A 17x8 or 18x8 et35 is a good suggestion for a more flush look but you will need to lower it really for it to look properly decent.