There is no information on its PH level for Castor Oil, sorry: ref http://www.jtbaker.com/msds/englishhtml/C1500.htm
So then we wouldn't have any PH info for FAI fuel either as it is methanol and castor oil.
Yes FAI types of fuel is the way to go, no nitromethane in it. But here in the USA most modellers are hooked on using some nitromethane in their glow fuels. Usually many engines in the USA market are designed to use nitromethane in the glow fuel too. These engines typically do not run all that well off of no-nitro glow fuels. You would have to modify them to work better.

As for gasoline engines, use whatever 2 stroke oil you like a lot more to choose from. Since gasoline engines don't normally run nitromethane, you won't have any problems.
But years ago the special synthetic 2 cycle oils were known to be hydroscopic and tend to absorb moisture. A lot of guys found out about that the hard way, after parking their 2 cycle motorcycles for the winter. Then when they went to use them in the springtime, the bearings were all rusted out and bad. So it goes to show that synthetic oils do not really protect a engine from corrosion on the inside. So that led to the oil companies using blends with synthetic and mineral oils as one solution.

Now as for those gasoline engines that have been converted to run nitromethane and methanol, you have the same corrosion issues from nitromethane. But usually these engines are used in racing, so they get taken care of really well. If it is a 4 cycle gasoline engine, you need fire protection systems in the sump to prevent sump fires or put them out. That can get exciting if it happens to you and you are in the drag car sitting behind the engine when it occurs.