continuing inconsistent mobile experience

On mobile browsers some users are getting a jumbled mess with text overlapping, header image not resized, etc, but inconsistently. For example, the site looks fine on Chrome, fine on Safari for some users, not okay for other users on Safari. Okay for a particular user at one time and later not. I tried updating all plugins, clearing the cache. I’m at my wits end. This has been inconsistently happening over months.

I posted about this a few months ago and was told to deactivate plugins one by one until I found the culprit. I did this, deactivated a certain plugin and it was fixed on my personal mobile devices when I reloaded the iste. Not 5 minutes later, a friend told me it was a mess on her mobile device, and I confirmed she had reloaded after my “fix.” I do not see how I can know if this issue is resolved when it looks fine on my own devices and appears I’ve fixed the issue… but my users are NOT experiencing my site correctly.

The page I need help with: [log in to see the link]