The Perfect wasn't Suntour's best. Their Winner freewheels were the best on the market way back then, (in a galaxy, far far away).
Sounds like the lube inside have the pawls sticking. I'd remove the freewheel and give it a cleaning. Submerse it in a petroleum distillate ([paint thinner, kerosene, benzene(toxic), gasoline(bloody dangerous) to degrease the guts. Remove all surface grime, and rinse thoroughly in water. Displace the water with WD40. Run enough into the freewheel body. See if the pawls are free now.
Complete the job by lubing the freewheel with a quality motor oil. Run it into the body with capillary action. (If you got the cash, buy some German-made Castrol Syntec 0w30 if you can find it.)
Remove any excess oil and reinstall and go for a test ride.
As for the chain, did you use a remover? Sounds like the pin wasn't seated on the plate correctly.
Pins are reused on chains from that era.
Only super narrow 9-10 spd chains require new and breakoff pins.