I got someone to help me take the variator off again (I was calling it the clutch) and we put it back together properly (the bearings were not seated properly in the case). Now the moped runs as it did before--better acceleration and top speed of 30-33mph, which is what it did before. The man at the hardware store matched the new belt with the old one. The new belt is, of course, a bit tighter. Putting the new belt on has solved the starting problem I was having--it used to take up to 5-6 tries to start the 'ped but now it takes 1 or 2, maybe 3 times to get it started.
If anyone else has developed starting problems with their belt-driven moped, I would change the belt first. The old one was really worn and had way too much free play. The new belt seems to be a stronger and better-made belt than the stock one. My moped has been running just great lately!
As always, thank you all for your suggestions and help!