1. The selector is not valid. However, achieving validity is quite easy, in tmpl / default.php you just have to have an action value for the form tag, which should be "#" in our case.
2. One click template change. It's possible to work out a single-click template change with template selector, but for this the users have to edit some code (hide everything in css but the next button). Would be great if you could add this feature for the next release, and then joomla users would have an easy template switcher for accessibility.
I give you four stars for the time being, but if you correct the validity and especially add the one-click template change, this plugin and module will well worth the five. Nicely done!