Your card is an nvidia. So it's cant be a crossfire. Crossfire is ATI or now known as AMD GPU's. NVIDIA are SLI. But I don't think you can do that with the 210.

Depends on what ram sticks you have. Do you have 4gb sticks installed or do you have the common 2gb sticks. Which would only give you 8gb total with all working correctly.

My Workstations can do 16gb also but they are ddr2 ram and 4gb sticks cost an arm and a leg. So I only have 8gb installed. It's not worth buying bigger ram. It's better to just put that money to a new up to date, kinda, workstation. The bigger faster ram is cheeper that the old.