May I suggest publishing the same content or at least most of your content both on Medium *and* on your own website? Best of both worlds - Medium authors could still submit to your publication, Medium members will still get your posts in the daily digest emails and feeds, and you can still offer the content for free (= ads supported) elsewhere. That’s what I do with some of my posts to reach both the Medium members as well as random Internet passer-by’s. You may be underestimating the power of Medium promoting your content and the convenience for the readers.

Good luck though, whichever way you decide to go.