Regarding ther Apple ID, the security set-up is designed to prevent you getting control of it, but you should contact Apple Support and ask whether there is a work-around. There may well not be because anyone could know the email address so obviously the security has to be strong. https://getsupport.apple.com
Transferring the podcast to your own account is also going to be problematic for the same reasons. There is a method, but it required you to have access to the feed to be able to modify it; and you have to contact Podcasts Support, and to do that you will have to be signed into the Apple ID - which you can't do in the first place. However this is the process, for what it's worth: poster tcarreira did this and has posted the method:
0 - Contact apple support from the current owner of the podcast: Contact Us -> Podcasts(My Issue Is Not Listed)*.
... wait for them to answer with further instructions and a code...
1. Insert the authorization code “xxxxxx” in the <itunes:keywords> or <copyright> tag.
2. Verify that your Apple ID is activated.
3. Obtain the direct link to your show on Apple Podcasts.**
4. Customize the statement below, and paste it in your reply to this message.
I authorize changing management in Podcasts Connect and access to Podcast Analytics to the account [Apple ID email address]. As requested, I have inserted the authorization code in the [specify tag] tag.
Paste the direct link to your show on Apple Podcasts
*Go to Apple Podcasts for Creators and click the 'Contact Us' link at the bottom of the page.
**To obtain the link in Apple Podcasts app (Mac - Catalina) find your podcast and click the three dots icon to the right of the 'Subscribe' button and choose 'Copy Link'. In iTunes - control-click (Mac) or right-click (PC) on the podcast image (or where it should be) and choose 'Copy Link'.
