Regarding the landscape problem then refer to these two articles which may offer fixes.
You could also try changing the meta tag to:
<meta name="viewport" content="width=device-width, initial-scale=1.0">
Which seems to be the one recommended for best results.
You'll have to point me to the page that is giving you the problem so I can try and test (I assume you are testing on an iphone). I believe ios4 had problems with landscape mode which has since been fixed in latest versions.
For the single cars yo can make the cars go full width like this:
The above are over-rides and should go in the media query for the smaller window width (around 750px).
It's really a matter of going through each element and changing height and widths and floats to a more suitable arrangement for smaller widths. There is only so much you can do with an existing design because when you start from scratch you can arrange things to work better. You can't actually change html with media queries so you have to make the best of what you can do.
You will have to point me to one issue at a time (with a link) as I get lost going back up and down the thread trying to work out where I am