My only source is real-life observation, though I’m sure some time researching online would be illuminating.

But, yeah. It’s worth a try. Try going completely without caffeine for at least a month, see if your sleep improves. Fair warning, though: it won’t be easy. Caffeine withdrawals are not fun. Lots of feelings of lethargy and headaches along the way. But after the first week or so, that goes away, and then you can live happily without caffeine dependency.

Personally, I gave up caffeine entirely* years and years ago, and I’ve felt much better since.

*Not absolutely caffeine free in all circumstances, though. If I absolutely need to stay awake – such as when driving late at night – I will occasionally drink one caffeinated drink to achieve that. But for me, that only happens once every few years or so. As long as it’s only one occasional drink, the addiction doesn’t really have time to take hold and it won’t cause long-term problems.