This shrimp definitely belongs to the Palaemonidae family. It could be a Macrobrachium but could also be a related species (such as Palaemonetes sp.).
It probably needs brackish water for its larvae, but to make sure you should see how large the eggs if they start carrying eggs. If they have a lot of tiny eggs, the larvae will need salt in the water. If they have a few large eggs, then salt is not needed for reproduction.
Your PH seems very high. I would recommend getting it closer to neutral, but you'll have to see how your shrimp are doing. Some shrimp can actually take high PH values like that but most don't.
The best long term solution for lowering PH would be to throw driftwood into your tank. Make sure it's driftwood that actually releases tannic and humic acids into the water (most should be doing that). Sometimes companies advertise that their wood "does not discolor the water and does not release any chemicals" which, in this case, is a bad thing. Avoid those.
I collected my driftwood myself from the desert in Arizona. Works like a charm.
its a substrate product that mr. amano himself markets and sells. Recently you couldnt buy this stuff in america, but now these guys are selling amano products:
Works like a charm. 