I think I got it fixed... The nub is worn and the stop holes in the frame are also worn, so it still doesn't snap in 100% in the off safe position but at least it won't flop around now.
There wasn't much room for shims or modified pins, everything actually seemed to fit well so I determined that bending the lever was the appropriate way to do it. I'm scared to death bending stuff like this, so I did it in a very controlled manner by clamping the shaft in a vise with the lever about 1/16" above the jaws, and then I put a center punch under the lever as a fulcrum. When doing it like this I can only bend it until it hits the vise, so there's no risk of bending it too far. I did that a few times, test fitted in between, and finally got it to work quite well.
The pin is tight in the lever but pretty loose in the hole, so I'll check my drill bits and see if I can find one that's slightly oversized. I have a cheap letter/number set that I bought for this purpose ($30 for all the pins you could possibly need...
), so it's just a matter of finding the correct one.