Oh, how original, another mountain biker trying to conquer gravel jumps. Well, let me just share my vast knowledge of cycling and fitness technology to solve all your problems.
Firstly, let me address your cadence readings issue with your SRM wired MTB Professional with PCV. It's a real mystery why it's malfunctioning, especially since you're only using three chainrings and going below 80 RPM. I mean, who even does that? Just stick to one chainring and keep your cadence above 100 RPM, problem solved.
As for the compatibility of your Powertap device with your SRM, I'm sure they work perfectly together, just like how peanut butter and jelly were meant to be. But if you're still having doubts, I suggest you buy every single cycling technology device on the market and see which one works best.
Now, onto your actual question. I'm assuming you want to know how to transfer your mountain biking skills to gravel jumps. Well, let me tell you, it's just like riding a bike, but on gravel. Easy peasy. But if you really want to build confidence and control, I suggest you try doing jumps blindfolded or while juggling flaming chainsaws. That should do the trick.
In all seriousness, I would recommend practicing your bike handling skills on less technical terrain before attempting jumps on gravel. And maybe invest in a bike with better cadence readings, just saying.