Hey there Alex,
Welcome to the forum & congratulations on being the new owner of a great bike.
The petcock is vacuum operated, but can be converted to full manual operation by dissassembling the vacuum diaphragm housing, removing the spring & diaphragm & then re-assembling with the spring on the opposite side of the diaphragm so the spring now holds it open vs. holding it closed. MAKE SURE THAT YOU ALWAYS CLOSE THE PETCOCK WHEN THE ENGINE IS NOT RUNNING.
Was the bike sitting outside with a tarp over it, or was it inside & out of the moisture? The aluminum rims will corrode & become dull looking with moisture & age. You might try some "foaming oven cleaner" on the rims & the engine. Do not let it get on the paint & have a hose with you so you can rinse it off after a minute or two. Simple Green may work also. If it is on the section of the wheels that are clear coated or bare aluminum looking, you can gently sand out the dull spots with some fine wet & dry sanding paper. Use progressively finer grits until you get to the 1000+ grit range, then use some "Semi-Chrome" polish. Check out what I did in this post:
http://ascot500.com/index.php?topic=122.0Brake parts are still available from either Galfer, EBC or Spiegler. Replace both your front & rear rubber brake lines with braided stainless steel lines if you can afford it. New SS lines & new pads is usually all the FT Ascot needs to be a great stopper. With only 2K+ miles on the bike, you may not even need new pads.
As far as an ignition switch with a matching gas cap key... You're going to have to search eBay. I needed the same thing a couple of years back & found what I needed on eBay at a reasonable price. Most parts for the FT Ascot are not very expensive.
Check out this forum as much as you can. Especially the FT Ascot "Tech Section"
http://ascot500.com/index.php?board=11.0Make sure that you read the "Essentials For The FT500"
http://ascot500.com/index.php?topic=10.0Call Mark at ThumperStuff
http://www.thumperstuff.com/FT500.html & introduce yourself as a new Ascot owner. Then place an order for the two jets that you need to change & either a 16 tooth or a 17 tooth countershaft sprocket depending upon how much freeway riding you think you'll be doing. I ride mostly back roads & went with a 16 tooth. If I commuted longer distances more, I would change to a 17 tooth. Mark also has oil filters, brake parts, etc.
You also need to pick up a real Service Manual for your bike. It will be the best money that you spend on your bike.
Good luck & please feel free to ask any questions.
J.