Wow, what a conspiracy theory! LHS's are pushing higher nitro fuel that people don't need in order to boost their profits. That extra $3 a gallon must be a really big deal!

The truth is that the fuel you have is good stuff and the hobby shop did you right. Your engine will run fine on lower nitro if you want to save a few dollars though, and you probably won't notice the difference in horsepower on trainers and most sport planes. You shouldn't go lower on oil content though. Cleaning the slimy castor residue off the plane is part of the flying field ritual for everyone who flies glow. Depending on your muffler location, an exhaust deflector might help.