Existing Website Layout

To get a fix layout on any browser, all my post contents are wrapped in tables.

Will these facts also cause problems in a paid version Mobile Joomla?

I tested the free version in my website and I'm not convinced.

No, most likely you will get the same result with the paid version.

Did you try to override table's width in the mobile template's css/custom.css file? (e.g. ".content table { width: 100% !important; }" or something like that)