At age 48, I just started riding dirt bikes in March of 2000. I have ridden street bikes for many years prior. I ride a '00 CR250 and when I first starting riding dirt bikes, I had a tendency to keep my weight (240lbs) too far back on the bike. On jumps (mostly small one to start) I found myself being thrown back on the bike which caused me to roll on more (if not full) throttle. Then like you, I'm hanging on for dear life.
I have since overcome that by keeping my weight forward so you can see the front number plate, even on small jumps. While seated, keep the elbows up, butt up against the tank, and lean forward into the power. I think we (new riders) underestimate the power of the newer bikes, especially when the power really hits.
So.... that is my experience as a "newer" rider. Hope the rib heals real soon and you can get back to practicing. Start out slow and practice using all 5 controls together. Speed will come with experience.
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cr250john
Mine '00 CR-250 - '95 Yamaha Virago XV-750
Kids '01 CR-80's