If your friend says I'm wrong, please tell me but it's my understanding that once pardoned, the target's 5th amendment right is gone, as pertains to the crimes covered by the pardon. I suspect Obama would have to pardon a lot more that Hillary to cover all potential offenders. Who likely know a bit about him as well as Hillary. And Congress, having a supervisory obligation, could easily continue to investigate these transgressions. As I understand it, a pardoned Hillary would testify honestly, or be jailed for contempt or perjury, or both. A politically unattractive position if Trump is elected, though he seems to want to "drain the swamp". And politically a pardoned Hillary could be as vulnerable as an unpardoned one.
Not to add to the complications, but a President can issue an amnesty to anyone/everyone, known or unknown, involved in a class of Clinton crimes. I have no idea about those legal details, except that it seems to be the power of pardon applied to a group.