Try blue rams horns... Just as good as the reds but prettier.
Very observant aokashi... Thats one of the benefits of the pond snails. Not sure if it's due to their shell design or what but they often hang on the surface to feast on the bacteria of scum if you don't have enough surface agitation.
Sonicpath gave away some really pretty leopard print pond snails last week.
Mts normally can get to the top along the glass and even beneath the floaters only to take a dive back down to the substrate. If mts are dying on you, it might be more due to being a new tank as there may not be sufficient food detris in the substrate yet. Another problem might be nitrates. I can dig up some older ones for you if u wanted to try them again dan.
The nitrates are fine in my rili tank. Maybe they don't have enough food in the substrate.