Well, it's interesting and surprising to read that. I gave up on slime tubes two or three years ago; have they changed in that time? I've had the Slime plugs blow out of the tube at pressures over 60 psi or so; I prefer to inflate to 80-100 psi.
Nor have I been able to get my patches to stick to Slime tubes. I use a Rema vulcanizing patch kit, and usually have no trouble using it; I think the tube in my back wheel now has like a dozen patches on it. When I patched a Slimed tube, the patch stuck fine, and held air for a few hours; but the next day the tire was flat, and the patch had come completely off the tube. Is that really just me?
By the way, I've taken to using tires with puncture resistant belts... it seems to help.
I had to clean the slime off for the patch to stick, I used some patch kit from the motorcycle store. It didn't ever come off. I don't patch often though usually if I have a large hole I just replace the tube.
I have had the slime plug blow out, but only with the larger hole that one time. It was a hole about 1/4 of an inch in diameter. I don't expect the slime to plug holes that size or larger. It just plugs smaller holes for me, like goat head punctures, which are the majority of punctures for me.