I bale with a 720 now, but used a 620 for a number of years. I always thought "2 turns was a suggestion or a starting point and have gone much further myself. The 620 is more temperamental to varying conditions in the hay field and moisture content. I'd say you got her runnin pretty good.
For parts, I've had good luck with Maibach Tractor in Ohio. (800) 808-9934 They are a helpful bunch there.