Let's see:
1. When you add brake fluid, you'll have to bleed the system. Careful with removing/opening the bleeder. Start soaking it in penetrating oil now, then replace it with a new one.
2. Fuses: left side, under side cover. Check them all.
3. Faulty electrics: could be a bad run/stop switch connection, connections behind headlight, lots of places. Troubleshoot the areas one-by-one and repair and grease all fittings. If in doubt, cut and solder on new connectors.
4. #3 cold - probably the plug cap. Check the fitting at the spark plug, and pull the plugs (keep them ordered) and compare them. Check for spark on that cylinder. Could be a bad wire connection to that plug only
Keep this in mind- you paid $500 and got a great bike; not a perfect bike. It's going to need some work and some elbow grease to make it reliable and safe. Do the 3,000 mile tune up on it. Make a list of things that need attention, and you'll get thru them quickly. Pull down the manual off this site and keep it for reference.
Also, make sure you adjust the valves, clean the points and double check all your bearings. Replace your fork oil too!