Ah, 80 litres is a bit bigger
For once, the shop advice was right. Male platies have one track minds and can harass females to death. With a 2:1 ratio, the females get time off while the males chase another.
Livebearer fry are pretty big when they are born; much bigger then egg layer fry from the same sized adults. I can see that ghost shrimp may be able to catch and eat newly hatched egg laying fry but I don't think they'd stand a chance of catching the much bigger platy fry, unfortunately.
Livebearer females are always pregnant if they have been in the same tank as a male for around 5 seconds during the last 6 months. It is virtually impossible to stop them breeding. As you are finding, the problem is what to do with the fry. With 12 adults, I assume you have 8 females? That's a
lot of fry
The Community Creator puts your 80 litre tank at 60% stocked with 12 platies. The question is, what else would be suitable for the tank which would eat fry. Any shoaling fish big enough would overstock the tank as you'd need at least 6 of them. The tank is too short for loaches and most cichlids, and the smaller cichlids wouldn't eat enough fry. Honey gouramis might eat some fry but platies would probably be too boisterous as tank mates. Peacock gobies/gudgeons (same fish)? They are more bottom dwelling fish than gouramis or platies.
To be honest, in your situation I would give serious though to rehoming some of your platies. Maybe cut them down to 4f 2m. That would cut the numbers of fry in half and give you room for more, fry eating fish. But with a 65cm length, you don't have swimming room for large fish, or very active small fish.