I don't think Tamiflu will have any impact on your HCV.
Viral Loads fluctuate all of the time. It is normal.
The tingling in your hands and feet could be peripheral neuropathy. Hep C can cause peripheral neuropathy. Of course, so can many other things. Plus, the tingling could be due to something else. But you may want to take a look at these articles about extrahepatic manifestations of Hep C: