1) You're absolutely right about this. Up until now we used the Fluid Infusion Reorderer to make it keyboard accessible. But this required us to have +7000 lines of code, only for this feature. Apart from that we also had some issues with it which weren't straight forward to solve:
. When using jQuery UI, both of those issues were solved.
The jQuery UI sortable plugin is currently being rewritten to have better support for ARIA & keyboard accessibility in general: http://bugs.jqueryui.com/ticket/7850
2) Could you be a bit more elaborate on this issue? Which browser/version are you using?
I've just tried it & made a screencast: http://www.screencast.com/t/18Xza5dbl2
but I can't see that dropping a widget into an empty column is very hard.