I think offensively you'd be better with FB than Flex. Make full use of that ATH with limited LP and PE, esp. if you're going to go 12-deep like you are this year. So before giving up on your current approach, I'd give that a shot first.
Also, check your fatigue settings on Leonard. He's playing too fatigued at many points in the games. Again, use that depth you have. I recognize you think he's your best big man, but his 66 ST is going to limit him obviously, but then I think you're overdoing it by having him play much too winded.
Also, why would you go slowdown vs. Mary Hardin-Baylor? And just normal vs. NJC? I think you're not selling out hard enough for 40 minutes of hell with your vastly superior ATH/DEF. And your ST is certainly good enough at this point to make it work.
Lastly, I'd put more distribution on your guards and have them slashing more to get to the line more. You're FT% of 67% is pretty mediocre for those grades imo, which tells me you're not using enough of your high ATH guards going to the basket and inducing fouls.
You're "75% all-in", but not quite there imo. Uptempo nearly all the time, switch to FB, reduce Leonard's fatigue settings (in fact, I'd have all of them playing at FF if they aren't now), get your guards slashing more and with higher overall distro.
REB will still be an issue, but I think if you can promote an uptempo style that gets the other team in foul trouble and makes them play their lesser players, this will mitigate some of the REB disparity.
Just my opinions...