No an expert, but.
Everett suggests sets of 3 for training the front squat, so maybe less reps per set. Shorter sets would need less recovery.
If the aim is to get weight on the bar, how about working up to a max single and doing back off sets ?
Is one session a week essential ? a session of sets ascending could help stop detraining.
What progression are you using ? simple linear progression (adding weight to all sets across) is harder than incrementing one set at a time.
From my limited experience, the limiting factor on the OHS is keeping the alignment necessary to maintain balance. Once you start to buckle at the bottom of the squat, the next stage is either stepping forward to stay under the bar or failing the squat and usually sitting down in the middle of the gym while everyone stares to find the source of the noise of the crashing bar.
The overhead squat certainly works the shoulders in a whole new way that nothing else seems to replicate.
Just to make it harder, try doing OHS with weights suspended from the bar. The added instability makes a difficult exercise even harder. Possibly it's of no benefit at all, but it does add variation.