Domain Mapping without Multisite

Hi WPMU Dev Experts,

I built and hosted for my client with Parallax from Themify -

I want to map my client owned domain to this site -

I do not have multi-site so I can't use the Domain Mapping plug-in.

I currently used Domain Forwarding and Masking on GoDaddy. Everything works fine on the desktop, however for some reason when I go to the site using from the iPhone, the theme doesn't seem to recognize that I'm coming from a mobile device and displayed the full site, which looks bad on the phone. Everything works fine if I go to the site on the iPhone using

Any suggestions on how to fix this mobile display issue while keeping the domain forwarding and masking?

If there's a better way how I can map the domain without using domain forwarding and masking and without installing multi-site or domain mapping plug-ins, I'm open to your suggestions.

Thank you so much for your attention!