Hostile client asking for global admin
We've had a client for ~15 years that recently has become quite hostile towards us. They've started asking for administrative rights to everything, taking issue with how we've been managing things, complaining about our cost, the owner stating "there's no way in hell I would have signed your contract" (his previous ops manager did).
I am planning to offer him a "break glass" global admin account if he agrees to not use it except in cases where we have violated our SLA with prior notice in writing.
In addition to this, I'd like to just get out of our contract with them. It's not worth this current headache. The complicating factor is they have a few open invoices.
I'm willing to let them out of their contract without having to pay it out (as it is written in the termination clause), but I don't want to offer this until we've received or are sure we'll get payment for those open invoices.
They've also asked for documentation and passwords to all other infrastructure. This was requested in the name of business continuity, which I understand. Would you wait until the termination of the agreement to turn this over as well?
How would you handle this?