Unexpected long delay to start review process and withdrawal of article
Today it is very difficult to find reviewers, especially good and timely ones, unless the journal is very prestigious or rewards them highly (eg with editorials).

Having said that, this journal seems to be handled poorly. Thus, I would suggest you to pursue another scholarly venue.

If your email was clear in stating that you were definitely withdrawing the manuscript, then you can submit it wherever you want already.

Be prepared though that they may try to dissuade you stating that the revision process is already quite ahead (which could be true but not necessarily).