Hi Steven
I have checked/tried 1, 2, and 3 from your suggestions without making progress.
I have been in contact many, many times with the web host (Netregistry) and they refuse to entertain the idea that the issue is with their server setup and insist that I should contact Apple, because it is a problem with iOS/browser (even though iOS/Safari renders the gallery just fine when the site is hosted with Zuver, the host I have my own server/test environment with).
So unfortunately, this remains unsolved and I am not inclined to spend any more time on it, rather I will tell the client he has to move web hosts and battle it out with Netregistry for a refund.
thanks for your attention!