Security measures

During a recent breakup, my newly purchased phone mysteriously disappeared. I need to log into a (joint) Google account my (ex)partner and I created last year. I'll be using my old phone and prefer he not know. What are all the ways I can cover my tracks?
i.e. Delete my activity on Google Dashboard's Web & App activity. Remove Access to/from the device I use. Turn off my Location and/or delete it in Timeline. Check Gmail for any "Suspicious Activity" email alert(s). What else??
Thanks everyone!