If you seem to be killing glow plugs there may very well be slop at the conrod/crankpin connection or between the rod and wrist pin. In my experiences when the engine will rev like that in the air it may very well be the tune. It sounds to me like you have either a lean HSN or a rich LSN or a combo of both to compensate for one another.

With the wheels off the ground if you rev the engine up high for a few seconds and let off the throttle does the idle drop down nicely on it's own? Does it start high and slowly drop down and almost die? Or does it just stay idling high for quite some time?

By the way... cool lookin pup! Is that a Dobie by any chance?