tightlines said...
Sounds like you might be standing a bit to far back on the board to me, when approaching a wave slow down (sheet out), bend your knees to soak up the wave and keep your kite down low to avoid being pulled off your board or getting air. Also avoid hitting the wave straight on, bear away downwind and hit it at an angle.
All good advice there-don't be afraid to get a wide stance going over waves-you can move your feet around heaps strapless so you get back to your trim stance after getting over the wave/whitewater.
Helmet is up to you-I don't wear one-just like to have minimal gear and don't like the loss of vision/sound/and the weight.
The bend ze knees advice is the best bet-it'll help you heaps going over waves and getting through chop-you'll find eventually that your upper body barely moves as your knees bend up and down taking the changes as you plow through the chop.
Good luck and enjoy.....