Blast was indeed 50%. Missle Mist is still available, and the website says it's 25% nitro and 22% oil. I used lots of MM, and often ran Blast in my ST .35C's in combat...never blew one up, either.
K&B was not as open about their fuel mixes, but it eventually came out that K&B Speed Fuel was 60% nitro. I used a lot of it in speed events. The early stuff was said to have a soybean oil in it, which I don't think worked very well. Later, they used "X2C" oil, which I suppose was some sort of synthetic, possibly UCON.
It eventually came out that Cox Red Can was 30% nitro, and I think Blue Can was 10% with 20% castor.
I started mixing my own fuel in '65 or '66 and mostly ran 65% nitro in speed, but some 75%, and always UCON oil. K&B Speed Fuel was the baseline, and easy to surpass, but we didn't know it was 60% at the time. I wasn't flying Combat anymore, but ran 30% and 40% in a Rat or two, with a K&B .40rr.

Steve