I want to mill acrylic from now on. Question: What speed (F) should I use and how much rotation (S) should I use?
Please answer.

If you spin too fast the acrylic will melt. Feed can be as fast as you want, subject to breaking cutters.
Really strongly recommended is to use some lubricant - not 'flood cooling', just a little lube, so the cutter does not drag. I use a mix of 3 parts kero to 1 part olive oil (skin friendly), but straight kero or even water might work. Check out "MQL" as well.

Cheers
Roger