I have a convict cichlid ~ 3.5" that regularly attacks an 8" bowfin.
Sorry for your loss. Male Bowfins are more tolerant than their female counterparts.
I have successfully kept dozens of Bowfins from fry ~ 1-2" to 20+ inches.
Here are a couple of observations that I have noticed.
1. I have seen a notable preference softer subtrate in the Bowfin's reaction. It has been to the point of clearly impacting the water column of the tank/ pond that I had them in. (Muddy/ leafy bottoms, they wallow in and spend the majority of the time in. Stone/ Gravel subtrates, the swim mid water column to top and take air gulps far more frequently than Bowfins given soft subtrate.
2. Outside of Florida with a few invasive species, Amia Calva does not co-habit with Cichlids. I am with you however, and have tried myself. If the Bowfin were smaller, or the male Convict cichlid bigger, I would have no choice but to move. I can't say that any cichlids are proper tankmates for Bowfins.
3. Common names for fish are horendous. I have NEVER had any pike family fish ever attack any of my Bowfins, and have kept chain, grass & redfin pickerel with them without incident. That "pike" is a cichlid, not even remotely a distant relative of a pike.
4. Venezuela crenicichla are notorious piscovoures as well as the Gar and the P bass. The Vene & the Pbass are MUCH FASTER hunters than the ambush bowfin. I have never heard any account attempting to minimize the establishing the suitable tankmate(s) for this very agressive cichlid in the tank first or at minimum at the same time.
5. Good luck, I am truely trying to help here. You are doing "?SOMETHING?" already to be able to get your gar in that tank with three much quicker agressive piscouvoures to get any food to it whatsoever! Any Gar expert will without exception strongly advise you AGAINST keeping that gar with those cichlids.