Super cautious Jeanne offering her two cents.
I am terrified of botulism, and checked our canned goods very carefully, but there were surprises everywhere.
I once opened a can of baked beans that looked perfectly okay, except for a small dent. The contents exploded out of the can - well, that was a pretty obvious indication that the contents were full of toxin.
Rusted cans are not necessarily a problem - however, the reason that rusted cans are suspect is that the rust can introduce a pinhole leak in the can, allowing botulinin spores to grow and produce toxin. That same pinhole leak can allow some of the pressure to be reduced so you might not notice any bulge - or there is toxin but not so much that the pressure has built up yet. Same argument for dented cans - the dent might introduce a small failure along the can's seam, for example.
Not much help, is it? My paranoia meant that I would boil any contents of canned food for a minimum of 5 minutes in an open/uncovered saucepan. The boil to last for 5 minutes.