my tip is to not use tabs, especially on mobile browsers. Either use separate layouts or do a long form view that allows a user to scroll down the page.
This is more on par with mobile design than it is just a preference. Take a look at any list -> form type app for iOS and the tab object doesn't even exist.
Latency is usually hand in hand with your ISP. Unfortunately not much you can do aside from upgrading your internet connection. If you want to test for this there's a number of filemaker hosting companies that offer a free trial. You could throw your file up pretty quick and test it out on another service provider to see if it is indeed your internet connection.
Your suggestion are good and I agreed much on these.
The actual problem I wanted to highlight here is the tagging order is not following well in iOS browsers (e.g Safari and Chrome). It works fine in FMP and desktop browsers.
It's an issue related to webdirect on mobile browser. We may need to file this case to FileMaker.