It says in the Hydro boost section, excessive effort may be due to a pressure problem from the power steering pump.
There is a gauge that is obviously needed J5176-E (highly expensive) and a procedure of checking power steering pump pressures in different situations. However, I think this would be done if you found that brake fluid pressure were low.
The brake system pressure test is much easier to test and the gauge to do so is dirt cheap. I bought one years ago from Summit.
Oddly enough the manual never mentions the brake fluid pressure range of operation. It merely refers to the brake pedal pressure required to depress the pedal.
Unfortunately the brake pedal effort gauge is J28662. is over $450.
You could ignore all that and obtain the brake system pressure tester from some where like Summit
https://www.summitracing.com/parts/ssb-a1704/overview/
In the kit it lists typical pressures. If after testing you feel it is low, then maybe go from there. I don't know what you could do to increase the pressure if all the components in your vehicle are working within design specs. But obviously if you are in the lower end of the operating range, you may be able to bring it up.
The power steering pump incidentally has a pressure relief valve in the back of it that may be sticking. Perhaps you could replace it and see what happens. I wouldn't think it is very expensive.
Good luck to you