You're right about (1), I took a before/after screenshot (top: FF28; bottom: FF29): http://i.imgur.com/AJlgeBZ.png

Please note that I normally use tree style tabs (https://addons.mozilla.org/en-US/firefox/addon/tree-style-ta...) to put the tabs in a sidebar. It may have messed up the layout a bit. (also, the non-standard colour comes from ColourfulTabs)

I noticed that you used to use the URL bar on top layout as I did. Sadly that is gone now but the Classic Theme add-on will give you the option back.

To me it's just more visually intuitive to have the tab right above the content window, not over all the toolbars. I really can't fathom why the reverse has become the default.

Actually I put them my tabs on the left (default option with tree style tab), as I feel that putting them at the top or bottom of the browser waste space. I put the tabs under the location bar out of convenience, my purpose was to look at the difference in the tab size.

In terms of intuitiveness, it actually makes sense to have the tab bar over the address bar and navigation buttons, as their content and functionality are specific to that tab, and not application-specific. That's the reasoning anyway.

Absolutely right on same space but illusion of more. It's amazing how much small tweaks can make a difference in perception of visual space and faster action: bigger targets, whether actually bigger or seemingly bigger, make users faster in hitting them.