Cannabis, alcohol, caffeine etc. most definitely suppress/ prevent dream recall. They can have effects on memory months and years after completely stopping.

Dietary choices and environmental exposures that lead to waking memory loss/ alzheimer's (which is considered a form of diabetes) affect dream recall. My theory is that this is why it's typical for dream recall to weaken as people get older.

I'd say make sure you're 'clean' for at least 6 months with regards to the above stuff before asking these other questions. The questions you're asking are fun and interesting to contemplate, particularly when under the influence of substances, but it's impossible to get a clear picture when you're choosing to ingest substances that have a powerful effect. (I'm a former daily cannabis user speaking from experience.)