It seems to me if your thread is old and breaking, unless it is the only color of it in the world, I'd toss it and buy another spool. Why spend hours trying all kinds of things to try and fix it. I'm thinking that even I, who have been sewing for nearly 50 years, don't have so much rotting thread I have to replace it all, so the cost to replace the bad thread you DO find is probably going to negligible.