With my limited understanding of the piece and rulings I believe it goes like this:

Here is the scenario: You have Carrick getting haunted by Anakin Skywalker, Force Spirit and an Obi-wan Kenobi. It is initiative you roll a 11 which activates Karmic Luck (Giving any roll you make +4). Your opponent rolls a 12. He decides to go first and attacks with an Imperial Knight and kills Kenobi and you put the Light Spirit 8 on Carrick. Then Roan Fel attacks Carrick and the attack is successful. You then use Lightsaber Block and roll a 4. Because you got an 11 for initiative the roll is actually an 8 but still fails. You then decided to re-roll the save using another force point and because you were given, in essence, MoFT 2 by Kenobi dying. This activates Mettle from Anakin Skywalker, Force Spirit and Karmic Mettle, because they are two different abilities. This combined with your Karmic luck gives you a +12 to your roll. You roll a 6. Which because of everything going into it is enough, 6(base roll) + 12(modifiers) =18, to get off one of those oh so delicious Cortosis Gauntlets.

If that didn't answer your question I apologize and truthfully you may want to what for Sithborg or another experienced rule person to answer.

As a side note, concerning Reserves. The interactions between Karmic Luck and Reserves are not related, I believe. If you are wondering about rolling an 11 with Lobot and getting 30 points and bringing Carrick in at that time whether he gets the +4 I do not know.