+John Baez "When in doubt, Goole it out." G+ defaults to have jetpack cross posts only seen by you (private rather than public). You can change this by following the details at https://jetpack.me/support/publicize/google/ and following the instructions under "Changing who can see your Publicized posts on Google+". For self-hosted blogs, you're somewhat limited in what/how things get posted to G+, most of them tend to be the "title" and the "excerpt" portions of your post, though within the publicize portion of the "publish" block, you can also enter a custom message that will override the "title" if you wish. You also have the option to add a "featured image" as well that will add some visual interest. From self-hosted blogs you can use modules like "All in one SEO pack" to better customize what gets ported over to social media platforms.

Ideally, you should be able to post enough to help remind your obviously devoted G+ following to click through and read the details on your blog, so that your readership doesn't suffer as much as going cold turkey. Those who are seriously engaged will take the G+ posts as a reminder to come and read your material (and honestly this is most of the reason that platforms like Facebook and Twitter took off in the first place.) Given your reach here, you might also find it easy enough to get a Twitter account, plug in your addressbook and mass-follow those you know and similarly "ghost" post to Twitter as well. You may find that you can vastly improve your reach and readership doing this.

Naturally, if you wanted to, you could manually cut and paste most/all of your entire post with a link to your blog, but this is probably more time intensive than you'd prefer.

From a PR perspective, you're taking back most of your "John Baez Brand" from Google and moving it to something you directly own and control. I'd also recommend that you encourage your readers to go to the siderail of your blog and simply sign up via email as I'm sure most all of them live as much in email as anything else. Then instead of relying on not missing anything in the flowing stream of G+, they'll get a physical notification of everything you post and have the option of not missing as much.

Feel free to call if you need specific help. I hope I'm easily enough found on the web.