> Simple gestures for Android is full of other options that you need to disable one by one, then enable only pull to refresh, it's a pretty tedious process.

I understand what you mean — it’s definitely tedious to turn off everything just to use pull-to-refresh. I’m planning to release a separate extension dedicated only to pull-to-refresh. I had paused the project for a while because of some bugs and lack of motivation, but I’m planning to restart development. It may take some time before it’s ready, though.

> Ideally I should be using a longer delay window and have the ability to swipe up to cancel it.

You're absolutely right — there should be a way to cancel the gesture by swiping up. I’ll fix that in the next version (it might take a little time for Mozilla’s review process).
For now, you can actually cancel a pending gesture by moving your finger far enough upward (or sideways), so please use that as a temporary workaround.

> I'm not sure that extensions can interact with an empty web page.

Yes, you’re correct — the extension doesn’t work on blank or failed-to-load pages. I’ve confirmed that extensions can’t interact with empty web pages, so this behavior is expected.

Thank you very much for your detailed and thoughtful feedback!