yomama - caspercarver asked me to join in a bit ...
1) When going backwards you also have to turn around the weight distribution. Nevertheless I never have as much weight on my front foot (my normal back foot) when going backwards than I have riding normal. So there is not as much pressure on the tail when riding backwards. Therefore it doesn´t dig in that easily.
Remember all the exercises and phases you went through when you learned snowboarding and try to relive them when going backwards.
I can´t even remember when I learned it (so long ago) and I have used loads of different boards, but I never had a serious injury.
And don´t be afraid - in inhibits you too much! Stop thinking and follow the flow
2) Falling - try to do the same thing you do when you normally fall - stay low, when falling backwards try to make a "round" back, use your whole arms (and not just your hands) to dampen the impact.
About your bro - crashing at slow speeds on fairly flat ground is often more painful than on steeper slopes where you just "roll down".
3) Sounds great! Learn the jumps when going rather slow and across the slope, jumping off the edge. When you feel comfortable, try to go faster and more down the fall line. Learning on the Dual is a great idea! And then just do the same motions on the Extremecarver. Despite the higher angles, you will be surprised how similar it feels

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Keep it up

!!!