Looking for tips to increase mobile friendliness

[pjkcards]

I want to work on the mobile friendliness of a site. Currently I have m.domain setup, though many users use the Tapatalk app to view the content (which means I'm not doing a good job with the mobile side of things).

I have these 2 vB settings set to my mobile style, but for some reason when I browse to domain.com on my phone, it doesn't go to the mobile style, not sure why:
Default Style for Old Mobile Browsers
Default Style for Modern Mobile Browsers

In the lightweight style options, I also have my mobile style set.

When I ran the Google Webmasters Mobile friendly tool, it fails.

It fails because it is loading the desktop version (shouldn't it redirect?), and I'm not sure why.

Any tips to improve what I have or change to something better would be appreciated. I need to radically improve the mobile usability on the site. Thanks for your time and help.