Unfortunately, this will be hard for me to debug as I do not have an iOS 7 device or access to your theme (which is not free, so I cannot download it).
It is certainly a mystery why loading the 'simpleviewer.js' file should break the responsiveness of an entire web page but only in Chrome and Mobile Safari in iOS 7.
Running your first 'Wedding Dresses' gallery web page through the W3C Markup Validation Service (to check the page's HTML code) reports 65 errors and 90 warnings. I realise that your page seems to be rendered OK (even with these errors and warnings) without WP-SimpleViewer being active but what if the problem is somehow caused by a combination of these validation issues and WP-SimpleViewer (ie. the problem only appears when both the validation errors and present and WP-SimpleViewer is active)? How would the web page look if WP-SimpleViewer was active but there were no validation issues on the page? Perhaps you could tackle the validation issues to see if it makes a difference. (The errors should really be fixed.)
Additionally, running the same page through the W3C CSS Validator (to check the page's CSS code) reports 17 errors which, again, should be fixed. (The warnings reported are mainly browser-specific code and may not be such a problem.)
Also, it looks like you may not be using the latest version of your U-Design theme. (It looks like you are using v2.0.1.)
Try updating it to the current version (v2.1.0) to see if this helps.
Another thing you might like to try (just to see if the same thing happens) would be to use WP-Juicebox (an HTML image viewer) instead of WP-SimpleViewer.
I am not suggesting that you change image viewers but it might be interesting to see what happens when you deactivate WP-SimpleViewer and activate WP-Juicebox instead. (The interfaces are similar for both plugins so it should hopefully not take you long to create a test Juicebox gallery.)
WP-Juicebox can be downloaded from this web page.
SimpleViewer Support Team.