The B100P looks good! You've saved it and got it running again, that's the important thing. I passed my bike test in 1981 on an identical model (even the same colour).
I think I only ever saw 65 on the clock once, on the legendary Beeford straight in East Yorkshire (on the A1079 to Bridlington) so if you can see 60 on the speedo, it's fine
They never had much power, and the delivery is like an MZ, just rev it through the gears until it goes flat then change up. As mentioned elsewhere, abusing the silencer with mallets, plumber's tubing and old bowden cables fixed in a drill chuck will ensure it's giving all of its mighty 10 (claimed) BHP.