Been out of the game for a while but I would suggest the transmission forum to find out what is the "hot" fluid of choice these days.....as far as RPM that will be dependent on your cars setup.
I used to run Mobil 1 which has a flash point of 428°f, however a lot of trans builders (back then at least) felt synthetic atf reduced friction too much reducing friction and sprag life (I never saw a problem).
A lot of guys used to run hydraulic fluid which has about a 20° higher flash point...but I have never used it.
All that said, the days of having to stand on the throttle/brake for 8 seconds trying to build boost are long gone so I am not sure how much of an issue flash or boil point is these days compared to 6 yrs ago.
Thank you. My learning curve tells me to use a full synthetic fluid and change it after each weekend. I have not tried the Hydraulic oils because everyone says they stick so bad after a couple of passes. Leaning towards going back to TCI. I tried the HPL and it was cooked after the 3rd pass.