VP = VP Racing Fuels, one of the biggest names in racing fuels and makers of the popular C-16. Any speed shop or serious race building shop knows VP. Just find a speed shop or race outlet that sells VP fuels or can get it. With VP methanol, you do not need any additives. Been using VP meth for quite some time now w/o additives but with alky/meth tolerant containers, teflon-lined hoses and brass fittings and no sign of corrosion anywhere. BTW, a gallon of denatured alky in Home Depot is $10. I buy meth 5 gal at a time and seems to last forever. I store it in a heavy plastic well-sealed container (not the cheap red ones) that is covered to avoid any light. Never had a problem.
As for the AFR, that is an interesting discussion. The actual AFR you run will vary with the combo but here is the rule of thumb I use and I still do not have it nailed yet but the car is running fine. Methanol will typically have an AFR about 50% of gasoline which also means you need to run twice the volume. I know approximately how much fuel I use in a single pass and I also know how much meth I inject. I use to tune for 11.0-11.2:1 and think that might be a tad lean and will start tuning for about 10.6:1 as I estimate that 20% of the fuel I use on a pass is meth. An engine that is more efficient might be able to run 11.2+. I use a very simple approach to tuning. Tune to the targeted AFR with no knock and that means you need good tuning tools like a WBO2 and datalogger. If I am rich I pull gasoline and if I am lean I add meth.
Keep in mind that you do not use any alky/meth in normal driving so normal gasoline tuning is done in that driving range. As the RPMs and boost rises, then pull gasoline from the tune as the meth is added. Of course, this is where the beauty of aftermarket engine management, WBO2 and datalogging systems come into play.