This may be a stupid question and in no way am I directing it at the OP as I feel your pain on the sail work (going through the same thing with my furler and rigging now myself)
But how exactly does the sail unfurl itself in high winds? When I roll up my sail I make sure to roll it up so that it has about 3-4 wraps around it with the sheets acting like a sail tie I guess. Also before I coil up the sheets in the cockpit I make sure they are sheeted off fairly tight to a cleat so there is no way they are going to ease up. Also I make sure the furling line is well secured to its own cleat the everything is rolled up tight and cleated off so it can't unwind.
I am just curious if this is what everyone else does/what you are suppossed to do and how the sail could come loose from that?