I have no doubt he lied to the FBI, which is a felony...and not a BS felony especially given the fact he was specifically warned ahead of the interview to not lie. That said, I doubt he's a danger to society at this point so locking him up is probably a waste of taxpayer dollars, but a commutation would have accomplished that. The only reason Trump elected for a full pardon is b/c Flynn was loyal to him to the end.
Trump pardoning him just draws more attention to the fact that Trump hired so many people that ended up being criminals. Pardoning those criminals totally undermines all the "law and order" BS he and his supporters spout. It's Trump just doing more damage to his (and thus the Republican) brand. So i say he should pardon Manafort next for the same reasons...it would serve to remind everyone (again) how corrupt Trump is on his way out.