OP here. Just got back from SCI and a guy caught a 200 lber on the flatfall. He was rigged with a big single J-hook. Here is a shot of hook placement. Bled him out during the fight which helped get him to the boat. Note the teeth rubbing on the line. Don't be afraid to go BIGGER with that flouro leader.
The boat had a few flatfalls get chewed off on the drop. And one had a hook get ripped off the lure. Make sure the hook eyelet is welded shut. These fish will exploit the weaknesses in your gear. Err towards bigger and beefier when possible.
Clearly you can rig them different ways. The way I was taught by guys back on east coast speed jogging Japanese style was to use split ring, the assist hook was made using Dacron and a much larger hook, attach assist hook to split ring... then you attach top of the jig to the split ring.... this way you can swap out different color and size jigs easily. Those hooks you used look kind of small, not sure they hold up long term. And you definitely only need one.