As a starting point in a PA28 I'd agree with most of that. With practice, you'll get used to adjustments, just as I'm sure you did in your military flying.
One thing I disagree with is the proscription against extending downwind. A great many airfields prefer this as a means of ensuring spacing. I do agree however that widening the circuit is a poor practice. Some airfields also prefer orbits for spacing, but those need treating with care because it can just mess everybody up behind you.
It is very "flying by numbers" mind you, which is perhaps appropriate to military training or airline flying, but light GA does both allow and need a bit more flexibility on speeds / power settings / turning points, particularly if e.g. you find yourself sharing a circuit with a couple of microlights and a helicopter, as well as the usual mix of fixed wing traffic which might have downwind speeds from 50-110 knots, requiring care and flexibility from everybody. The pilot insistent on flying an absolutely standard circuit regardless of what's going on around him will make few friends!
G