Harmonic balancer comes off

The washers are kinda rough looking from the factory. If it is essentially flat, then it should be OK.

The longer bolt sounds like it was put in there because somebody in the past lost the 6th bolt with the 'spikey' star washer. I'd make them all the same. Won't hurt you to get a new set of 6 new grade 5 bolts of the right length and star washer for each.