Do you wish to share to DKIM settings so we can review and give advise... Otherwise, any suggestion can't be grounded in science. Also, everyone should pledge to NOT send any eMails -- just observation ONLY!

You can check DKIM settings by emailing yourself at a Gmail account and using the show original option.  There are also DKIM test sites, where you send a message to a unique account and the web page reports results.  But other factors also come into play.

Do you have a DMARC policy, and if so, what p= setting are you using? 

Are you getting DMARC aggregate reports?  Yahoo sends them if you have the feature enabled.

Have you created a Yahoo account, set your other account as a contact, and sent test messages?   Once you are their user, you can complain about missing messages