First, I'm not sure, but jello is not usually a culprit for chest pain? Have you contacted your doc with this info?
Second, regarding the timing of bites:
I got mine down to a science. I'm also pretty anal, so this may be too extra for you, LOL:
Take one bite
Wait 3 minutes (I used the timer on my watch).
Ask myself: Do you want another bite?
If yes go to Step 1.
If no, go to Step 2.
If I have answered no to this question 3 times in a row, I'm done eating. Go to Step 4
Put your food away in the fridge and try again in an hour or 2.
Goes without saying, it took me a pretty long time to eat a meal in the early days. And I got used to cold/room temp food pretty quickly.
These days (2.5+ years out) I take 2-4 bites at a time and just wait a minute or so without the need for a timer. Sometimes I don't do this as well as other days and l'd pay the price either in uncomfortable chest pressure or barfs.