If I am entering in a BF against a ksante, that later plays Ntofo strikes (which would kill my attacking unit), does my own unit deal damage to ksante before tactical retreat resolves to save my unit and go to base?

No — your unit is recalled during the Combat Showdown, so it never reaches the Combat Damage Step and K'Sante takes no damage from it.

Ntofo Strikes is an [Action] spell, so K'Sante's controller can cast it during the Combat Showdown, well before damage is assigned (Rule 467.2 only happens once the Showdown closes). Your Tactical Retreat resolves first and sets up the replacement effect, then Ntofo Strikes deals its damage — your unit would die, so instead it's healed, exhausted, and recalled to base right then (the recall is not a move). With no attacker left at the battlefield, there are no attacking units to sum Might for, so nothing gets dealt to K'Sante.

This is the opposite case from FAQ #11854: Tactical Retreat only "saves" a unit's combat damage when the lethal damage actually comes from the Combat Damage Step, since that damage is dealt simultaneously and the recall happens afterwards. Here the kill comes from a spell in the Showdown, so you leave early.