PVC is quite similar to ABS, perhaps a tad softer. Both are fairly abrasive to machine so your HSS will lose its sharpness quickly. On an ABS production job I ran a 3/4" carbide mill at 3k and around 120-150 ipm profiling and pocketing. I would start around 2k spindle and 50 ipm and go up from there. Increase the feed until the surface finish is too rough before increasing the spindle speed. As others have said don't think about chip load, soft plastic is totally different to machine. Use a very free cutting mill, aluminum types are ok but those specialty routers for plastic from Onsrud are several levels above aluminum type mills for plastic. Kind of like going from mills for steel to aluminum specific for machining aluminum, a real eye opener. I use 2 fluters vs 1 flute and have had no issues. The only downside of the Onsrud tools is the surface finish on pocket floors is poor. Harvey makes the plastic specific routers too but they are twice the price.
Plastic is usually difficult to hold so that maybe your limiting factor.
I find I can machine plastic twice as fast with flood coolant vs air so prefer flood. Burning plastic is bad for your health, nothing special about PVC in this regard. If you were molding it then it is special, if left in the barrel too long it can go boom.