You can also fashion a guard to protect the air filter, by attaching a piece of plastic to the frame with zip ties. The idea is to keep the air filter out of the spray zone of the rear tire. I like the 90 degree turn idea, and I'm looking forward to seeing it.
I would abandon the headlight idea, since the coil is not likely to be able to power it, or charge a battery. Wait for you next bike on that.
That seat looks awesome! Did you recover it yourself? I'm sorry to report that the flat black tank will not last, because gasoline vapours will pass through the tank and peel the paint. Better to buy a tank in a colour you like.
You'll likely find a replacement rim on eBay; hopefully it will be in better shape.
Yes, that's the tire size. Try eBay,
www.rockymountainatvmc.com or
www.bikebandit.com