I would check with the manufacturer of the bit. (festool bits have the max rpm printed on the shaft)

Whatever speed you pick, I would take shallow cuts.

Could be is very different than should be. I really don’t like large diameter router bits, but then I am the cautious type.

Great chart, @ Cheese!

I would slow the bit way down and as others suggested, take several passes. Do the end grain first and then the long grain sides. Slow even feed rate too.

Good luck!

I've never really worked out why the manufacturers don't just put the numbers the same as the speed x1000 so speed number 7 would be 7000 rpm and 23 would be 23000 rpm.
How hard would that be?

Some of it has to do with the wood itself. Some species are much easier to machine than others.
The chips that come off of the cut will tell you a lot, but again varies by species.
You really want to minimize the dust in favor of shavings. It takes some experimentation, which is the reason for the range in the charts.
It is just as possible to go too slow as it is too fast. It is probably best to start at the low end of the chart and work your way up, to see if it gets better.
Feed rate goes along with this too. Moving too slow is just as bad as spinning too fast.