card says you can discard a card for combat check
-if that card is a spell, can you recharge it instead?
-if that card is just a boon, can you recharge it instead?
No and no. You can only recharge cards when using them for their power, never when paying a cost for another power (unless that power specifically requires recharging a card), or discarding them for damage.
Lastly, you get a barrier that causes you to summon a henchman, if you defeat it can you try and close the location?
No. Only when you encounter them in a location deck. This is specifically mentioned in the rules.
Under "Summoning and Adding Cards":
If the summoned card is a villain or
henchman, defeating it does not allow you to close a location or win
the scenario—ignore any such text on those cards.