Great stuff
BrazililaCaptain! I'll just point out a small error that may confuse those who read it. In relation to the PCU you say,
One side is pressurized with metered oil pressure, which doesn't change when the engine is operating normally. On the other side, is metered pressure.
Presumably the bolded bit should be supply pressure (the Dash 8 manuals refer to it as "constant pressure".)
The beta control in the flight range of the power lever arc is referred to by deHavilland as "flight beta".
The Dash 8 manuals were never very clear on how any of this worked, partly because it is vastly simplified compared to what you have written and also because it doesn't adequately explain the difference between the oil pressure that is directly controlling the blade position and the metered vs constant oil pressure that is inside the PCU.
Anyway, I understand it a lot more now than I did before thanks to your post.