After trying to keep the park tool in place this morning with a clamp, and it still springing out of nut's slot, I am starting to think that FB's words about chainring bolt being cheap are very wise. I think I will let it be for right now, and will put a note to buy some chainrings bolts in the near future. Next time crank comes off, I will drill that bolt out.

At this point, idea of truvativ dual-hex chainring bolts is very appealing

Thanks, guys!