Pepper spray, including the stuff for bears, is one item or category of chemical irritant (basically). Mace, CN, and CS, are not the same as pepper, although I have heard of combinations of them with pepper. If one reads the package label with Mace (which IIRC was CS, although that has to be close to 30 years ago) it explicitly says to not use it if being attacked with any weapon, including feet or bare hands. That's a clue.

I think dogs do have a different structure in the various mucous membranes of the face, but not enough different that pepper won't work. It is not necessarily reliable enough, soon enough with a motivated/violent dog (or person) - which for the OP is not an option. Portions of seconds count.

Most pits, even if horrible with other dogs, are very friendly with people (See Call44's report above). What we see in problem dogs identified as pit bulls is often some mix, or another Molosser breed. Breed identity is not actually important - it is conduct. Contrary to the old folklore, pits don't bite harder than other dogs - bite force is a direct function of size, and their jaws don't "lock", either. They do, however, have the tenacity of the terrier breeds. Ever seen one of the other terriers on the hunt for rats, etc.?

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NHI, 10-8.