You can get KNO3 (monopotassium nitrate) shipped in individual 1lbs bags. I would not order more than 3lbs though, otherwise they might think your building a .....

An electronic solenoid is a must if your going with pressurized co2.

I would not mix the different varieties of shrimp. Just keep it as the same and no mix breeding will occur. Not every type can breed with each other. Crystal shrimp and Red Cherry shrimp can breed together.

I had guppies successfully living with cherry red shrimp with no problems. But, the new borns will get eaten by the fish. Just make sure you have lots of crevices in your driftwood for the shrimp to hide in when they are new born or molting.