Cherry shrimp really do best with 6-8 GH at least.
No Planaria could have killed off planaria, nematodes, detritus worms and scutariella (what most people probably call vorticella). Should kill vorticella, too. Cyclops are harder to get rid of... hopefully, the CPD's ate all, but I wouldn't be surprised if some are just hiding.
For future plants, you may want to consider an alum dip or bath. Alum makes the water acidic and I've heard of people using a bath for 3 days to kill off snail eggs. (not sure how well sensitive plants do with this)
Some people recommend Potassium Permanganate to remove pests, however, in my experience, it doesn't work. I did two PP dips on some plants within 24 hours. The second dip was so strong that it took *days* for the solution to turn clear. Snails never died...
Some people do bleach dips, although this can kill sensitive plants.
There's also Hydrogen Peroxide dips and CO2 overdose. Carbonated water could work for the latter.
So far, I've only dealt with nematodes, cyclops, detritus worms, small ramshorn snails, limpets and scutariella. A dog dewormer (Fenbendazole) took care of the scutariella.
Great pictures of your tank and shrimp!