'Corresponding author' (coauthor) is irresponsible regarding submitted paper. Should I step back from the collaboration?
You're overreacting.  Good collaborators are hard to come by, so do not do away with a collaborator unless you have an issue with the academic side of collaborating with this person, not if you have an issue with a journal.

First, if you want to establish priority, send to arXiv or an equivalent site.  Next, simply tell your collaborator that unless he/she contacts the editor or the journal very soon you will do it yourself.  Your collaborator may be corresponding author, but it doesn't mean you cannot yourself ask for clarifications from the journal.  Lastly, you will achieve nothing by removing yourself as an author.

Now... you are in a frustrating situation and maybe you are just looking for an excuse to pull out or stop collaborating with this person, but that's another problem altogether.