try to make sure you stay low and crouched if indeed you are going to get pumped, avoid diving off unless you're pretty sure that will give you a good chance of getting clear of your board and avoid going over the falls. To me it sounds like your probably only going to be surfing small tubes anyhow, so the best place to be as I say is low on the face if you can anticipate the closeout, this will be better than either A) going up and over the falls, potentially onto some sharp reef or rocks or urchins, B) straightening out is an option as long as you clear the lip of the wave, and youve got somewhere to go (some times you're gonna have dry reef which doesn't cooperate well with bare human flesh nor foam and fibre glass).
At the end of the day, copping minor beatings is half the fun, as long as you arent injuring yourself or damaging your equipment, getting comfortable with copping a flogging and taking it in your stride will be a benefit to the development of your surfing.
RE your board, mals are good for noseriding and cruising, but if you are after barrells then its time to start thinking about different shapes, for what I'm guessing is your standard is, this doesn't necessarily mean a shortboard, what you do want to do however is lose the platform nose, you can still have a board that is big and easy to catch waves on, but that big round platform on the nose of your board is a serious hinderance to controlled tube riding, so have a look around for something around the 7'6" - 8'6" mark, with pulled in nose and probably a rounded pin tail, definitely a tri-fin, a little bit of extra lift in the nose will keep it clear of catching, dont go crazy on the curve (rocker) of your board, the more you increase the curve, the slower it paddles.
something like a mctavish carver would work and is a proven performer:
pricey but reliable with good re-sale value.
You might even wanna go further in pulling the nose in.
PLEASE.
