Good stuff! I initially thought that you were just talking about a little past close hauled but you are going around 150 degrees instead of 100. Sure does seem like a technique issue.
When you tack, do you wait to cross under the boom until after the main has filled on the new side? And centering the rudders before you go?

Your analysis of time utilization is astounding. 1 minute of boat maneuvers for every 4 of good vmg type stuff. Are the courses that small? Are you tacking on every 2 degree shift?
I will have to look at that myself. If a tack is taking you 30 seconds to get back up to speed, that suggests you are on the tack for another 2 minutes. Interesting.