First of all the righting poles are made to right a two-person boat with two people. When designing it, the idea was not to single-handedly right a big boat like the Nacra. So, you may need a water bag system as well, if you are going to single-hand the boat.
As an aside, however, I would recommend you do not sail the Nacra 6.0 by yourself -- you could be asking for a lot more than a righting problem.
That is the reason I sold my Nacra -- lost a good crew when she fell in love, got married and had a baby. Now I sail a Wave and Taipan 4.9 (and it easily rights single-handed, as did the Taipan 5.7)
On the rivets, the pole should have not ve pulling on them, if you installed them properly. All the load on the rivets would be a side load and that would not pull rivet heads out.
I am not exactly sure how the Murray System works, but the idea is to cant the lever up, slip the knot through the loop so the bar is on an upward angle. Once set perpendicular to the boat, hand over hand to the end of the bar and right the boat.
If you cannot right the boat with your weight alone (test this on land) then you can possibly sleeve in an extension until you get the length you need to single hand.
Good luck,
Rick