Welcome Wayne t. The answer to all your questions re. hunting in Africa can be answered here. I went on my first Safari last August. We discovered this site about 16 months prior to our departure date and found it invaluable. Reading the Hunting Reports, loading data and looking at the photos will all enhance your desire hunt Africa.
Shooting competitively makes you a better shot, why would you cut back on it prior to leafing for your Safari? You will be expected to use "shooting sticks" but there might be an opportunity to shoot off-hand as well.
I wouldn't put too much stock in "the shots will be under 80 yards." Of the 23 animals my sons and I took, about half of them required shots over 200 yards.