OK, I'll take the first shot...
During an updraft (when you feel heavy), the rising blast of air hits
two major surfaces: your main wing, which is near the center of lift,
and the horizontal tail surface, which is way aft. The rising air will
therefore push the tail up, and that means nose down, to some degree.
The nose-down attitude will gain you some speed, since you say you are
holding the yoke steady (as opposed to holding the airplane level).

'Course, this can't work for long, since eventually you will have a
down-gust, which will reverse all that--you'' be nose high and slowing
down.

If you only run into the updraft gusts, consider getting a glider!!!
;)