Oh dear, it sounds as if the vet wasn't very helpful.
When I was a child, I had a tablespoonful of liquid paraffin spooned down me at the least provocation. It was also prescribed by our vet for one of our dogs when she was blocked up, 1 tbsp. again, so it sounds as if it's quite a flexible dose per kg. (the dog 'performed' the next day and was fine
)
The tooth grinding is of course a sign of pain, poor thing.
This doesn't sound much fun, but have you tried gently feeling round inside her anus, with a gloved and very well lubricated finger? You may be able to hook some faeces out, which could be enough to unblock the escape route. The least it would do would be to lubricate things for when she does go. But be very gentle, and stop if it increases her pain.
If she has no bowel sounds, then there's no point putting solid food in the top end because it will just back up. You need to get lots of fluids in, which is why I suggested the glucose, or honey, or sugar water, or something similar, which can be absorbed from above the bowel.
We're all worried, as you are, so do keep us up to date with events
