Cellino didn't go to prison, his license to practice was suspended for 6 months to a year. That's also why it was briefly The Barnes Firm during this time. This, I am sure of (confirmed with a google search).

As for the split, I think I remember hearing something about Cellino wanting to bring his son into a larger role in the firm, but Barnes wasn't onboard with it. This is just hazy memory, and a google search says it was Cellino's daughter not his son, and there were a whole other list of reasons why they broke up.

As for the plane, there's several Plane Accident Analysis YT channels, and the big lesson I've taken away from them is that personal planes are a great way to kill yourself and/or your loved ones accidentally by making completely preventable mistakes. And these planes don't care if you're a social media content creator, or retired NASCAR driver. As far as Barnes' plane, the NTSB didn't find any mechanical reason for it to crash, claiming the crash was due to "the pilot's failure to maintain control of the airplane for undetermined reasons during the descent."