I keep the females and male together all summer to get multi spawns...this year I needed a lot of Bettas to be ready this fall...so I artificially hatched a lot more than I normally do...I would steal the nest and eggs or I would wait until they hatched and scoop them up and move to a grow out......I would have new nest full of eggs about every 3-5 days.....due to the dark water and mass plants....I don't have problems with them hurting each other or eating fry....
Good plan with food...more varied the better...
I don't have too much issue with stunting hormone-as the the fry grow I move them to grow out containers, sunshine, active growth of plants and flushing the bucket when it rains or this year the water hose....lol.....
I have never used mystery snails....I use common-pond, ranshorn and trumpet....but I don't know why they wouldn't work too.....