"HELP" Power brakes very touchy

Prod length is not going to have any appreciable effect on braking force.
You need to check a couple of things:
- M/c bore is correct for that disc/drum combo
- the p/rod is in the correct position on the pedal. For power brakes it will be the lower hole if it has two holes.

If above is correct, & booster is new, I would suspect the valve in the booster. All boosters have some type of valving that modulates the force your foot puts on the pedal. With no way of modulating the force, you would have either nothing...or full on. I suspect that valve could be faulty.