I used to fly G-SARA too
Have you compared fuel flow rates for the same IAS?
The prop is almost irrelevant if one is talking about MPG in cruise. A fine pitch prop will deliver the same thrust as a coarse pitch prop, but will do it at a higher RPM and a lower torque.
No idea about the starting sequence. It should not be anything unusual - unless somebody invented something.
TB doors are quite good in rain because the rain doesn't go in (much) when you open them. They have to be watched in wind though - especially if the gas struts are knackered as they usually are in old planes.