Regarding the Modified FCC app, we have everything you need to get you going right here, a thread on this forum full of people happy to vouch for me:
https://mavicpilots.com/threads/mod-dji-fly-v1-4-3-ios-fcc-airsense-ma2-air2s-mini-2-1-by-gb160-gleno0h.90901/
One thing to be very cautious of...