I think the closing the gap part is to get your speed up to max but with newer freeride sails it is harder to close the gap. (see past articles in windsurfing magazine.) Before trying to head up you need max speed and then point up with your body forward.
As far as the second point in overpowered conditions I've learned to raise the boom an inch or two to get myself over the board when I've felt the sail and board trying to pitch me off. This of course is done along with tightening the downhaul and then the outhaul to try and depower the sail and maximize sail range. Never really thought of it as applying more downward force, just found that it worked to raise the boom.
Interesting articles though, I need to check out his web site. thanx.