Does spending a repair Command token count as resolving a Repair command for the effect of "Redemption"?

Yes. A command is being resolved by spending a dial, by spending a token, or by spending a dial and token combined.
(RRG, "Commands": "A ship can resolve the effect of a command by spending a command dial or command token with the matching icon at the appropriate time.")

One thing I am not entirely certain about is whether Redemption will give you "(Engineering + 1)/2" or "(Engineering / 2) + 1)" points for your repair command.

However I believe it is the latter, since it directly provides an additional engineering point rather than modify the engineering value of the ship. Dito for upgrade card Engineering Team.