A) Why can't you file electronically?  I know I've done it in Drake so I would hunt a little more for a ProSeries option.  You'll likely mark Amended in the VA module, hopefully that will allow a second efile but I don't know for sure (I left PS before VA allowed efiled amendments).

B) Good question.  The instructions are pretty funny, giving addresses for refund returns and balance due returns but not $0 returns.  I'd opt for the refund address PO Box 1498 since the Box 760 people grab the checks out for deposit then send the return on for processing.  It probably doesn't matter.

C) You probably don't need to file an amended return if there are no tax changes.  If the federal was amended (or adjusted), the IRS will notify VA who will then be looking for an amended return.  The easiest way to appease them might be to just file the $0 return anyway to head off the automated letter.

Rick