It is certainly possible to injure yourself with packing too much, just on dry land. Many people have reported this in DB and even I have experienced it. My best guess would be though, that the injury was not to the lung, but the intercostal muscles etc. I was sore for a couple of days and was examined by a doctor. He couldn't find anything that would indicate lung puncture, so he convinced me not to get an x-ray (just needless radiation).
He was of the opinnion that you could not generate enough pressure to rupture the lung, your epiglottis would give in first. But I disagree to an extent, since most divers who pack extremely full don't hold the air back with the epiglottis, but "the tongue block" or simply their lips.
Then of course there are people that are more prone to punctures because of structural differences and defects. There might be scarring due to trauma or sickness, which weakens the lung etc. It's perfectly possible to get a lung puncture by being completely passive. For such a person packing would propably be a very bad idea. At least before the lungs have been checked...
I would advice against "extreme packing" anyway. There are currently (to my knowledge) no reasons to assume it is not unhealthy. Moderate packing, up to the point of mild discomfort is propably quite safe. And if you do that long enough, gradually your packing amount will increase in a healthy way. Anyway, if you doubt that you have injured your self with packing, then it's always best to check it with a professional. Be prepared for some confused looks and explaining though, since the average m.d has now clue to what you could possibly mean by "packing so much my lungs may have popped". They'll just think you're insane
By embolism you propably refer to air embolism, which to my understanding is air entering the bloodstream due to over pressure or ruptures in the lung and the bubbles then causing all kinds of havoc (mainly, death) in the body.
