I can confirm that the stable channel of Firebug Lite does not currently work in Textastic 6 on my iPad.

But, when I open the website https://getfirebug.com/firebuglite in Safari on my Mac, I have the same problem: there is Firebug Lite at the bottom of the screen, but it doesn't respond to mouse clicks.

So it looks to me like this is a bug in the current "stable" version of Firebug Lite.

The good news is: the "debug" channel works! If I use this markup instead, it does work for me:

<script type="text/javascript" src="https://getfirebug.com/firebug-lite-debug.js"></script>

It looks like it is possible to convert TextMate bundles to Atom packages (see http://flight-manual.atom.io/hacking-atom/sections/converting-from-textmate/), but there currently seems to be no tool to convert from an Atom package back to a TextMate bundle.

It should be possible to do this by hand though, since it's basically just a different file format (property list instead of CSON).

Yes, for code completion, Textastic supports snippets including tab stops, placeholders, mirrors and transformations as described at http://manual.macromates.com/en/snippets