Thanks for testing the extension & the feedback. The first bug you mentioned is a known issue: https://github.com/hupf/tabmarks/issues/9 – I hope there will soon be the necessary APIs available to fix this.

Concerning the latter bug: I reworked the tab to bookmarks syncing. It should be much more robust in the upcoming 1.0.0.beta3 release (I hope Mozilla will review & publish it soon).