A client has caused me to miss the deadline for a project by being late on giving revisions. Technically, our contract is breached.

To keep it brief and as general as possible:

I have a freelance client who has delayed sending along the last round of revisions for a design project. This has caused me to miss the deadline outlined in our contract. Also per our contract, there is a clause stating the contract is terminated if the Parties were to not amend a breach within 7 days. It has been well over 7 days since the deadline stated in the contract and I have reached out multiple times to no answer.

Now, I'm pretty sure this client is wanting to ghost me and potentially steal my design without paying their remaining 50%, based on some of their comments prior to disappearing. So, my question is this:

Since the contract is technically breached and terminated based on the above info, do all the rights to the designs then revert to me?

And if I'm wrong about them wanting to ghost me and steal the design:

Will I need to send a new contract with updated terms to cover my ass legally for the remaining payment?

Thanks!