Good for you @SuperlativeScrubs
Right now I am secretly abandoning my current online accounts to cut all online ties to him (social media and forums etc) and making new ones. Reasons may become clear later on as it all develops.
Your bank account(s) OP? Change the security password (even if you think he doesn't know it) to something unique to you which he won't be able to guess. Make it hard to guess but easy for you to remember. Add a mix of special characters, numbers and capital letters.
If you work outside the home: let your HR/Payroll department know to pay your salary into your separate, personal account and not the joint account.
Switch off location on your smartphone. Do you have tracker on your car - can you turn it off?
Redirect your mail online. Google search Post Office Online Mail redirection. It takes 5 days to become effective.
If he knows (or he might know) your credit/debit card number and CVV (the 3 numbers in the back of your card) talk to your bank and explain the situation and see if they'll issue you a new card to your NEW address and stop the other card. Or See if they'll allow you to collect the new card at a brach local to your new address - ensure you bring good photo ID, eg Passport and/or driving license.
They'll ask you some security questions to ensure it's actually you they're speaking to including two or three transactions over your account and two or three parts to your "memorable" security info. Check you draw out enough cash and pay for anything urgent online before you do this though.
Withdraw at least 50% from any joint bank account before the other person makes it inaccessible to you.
Change your access to all shopping sites. Add 2nd layer security if possible - eg if you try and log into a shopping site you'd need to provide your mobile number and an access code would be sent to you so you can access your account.
Clear your browsing history if not already done. For further searches use the private or encrypted search which should auto clear (but double check) at the end of your session.
Good luck! 🌹