Is there a connection between late heavy suppers and my nightmares? Or is it just my imagination?

Answer 1

If you've noticed that those late heavy suppers happen to coincide with the nightmares, then it sounds like a reasonable explanation. You can always try to avoid those late heavy meals and see if that helps. (Or I suppose you could try only late and heavy suppers and see if you're right).
Even if you're wrong about it, it will add to sleep problems anyway. Beside, those meals will contribute to adding weight, so it'd be better to avoid them anyway (unless you are trying to gain weight).

Answer 2

Yes. You must avoid heavy suppers, because they WILL lead to a troubled sleep, and you'll eventually wake up feeling tired. Plus, you will gain weight: your system isn't given the time to burn the fat of the meal... So, avoid heavy suppers and heavy meals in general.

Answer 3

That, and you will gain weight.