how to stop flying fiber glass in attic, getting into everything

Nope. You're only real course of action is to remove the old defunct insulation and put in new insulation. The old stuff isn't doing nearly what it's supposed to do anymore and is actually costing you money to keep it by steadily increasing your utility bills and decreasing your comfort. If it's in the house, then the ductwork may simply need sealing everywhere.

- Or, patch the problem and screw the people after you, seal the ductwork and in the attic put a plywood floor over it, IF it's only between the joists. Or, if it's stacked up beyond the joists, then you can cover it with linen, craft-paper or butcher-paper. DO NOT use any kind of Plastic Sheeting or Foil, those will trap moisture from the house and cause mold problems all over.