The landlord tells me who I must share the space with but other than that his authority ends at the door."

My concerns are with the ERAP terms and conditions (below) that may prevent me from not renewing there lease; The property owner or authorized property management company must agree to the following terms as a condition of accepting rental arrears payments:1) The ERAP payment satisfies the tenant’s full rental obligations for the time period covered by the payment.2) Waive any late fees due on any rental arrears covered by the ERAP payment.3) Not increase the monthly rental amount above the monthly amount due at the time of application for ERAP assistance for months for which rental assistance is received and for one year from receipt of the ERAP payment.4) Not evict the household on behalf of whom the ERAP payment is made for reason of expired lease or holdover tenancy for one year from receipt of the ERAP payment.

Peter, you'll want to reach out to your local Housing Authority to get their steps. 

We would need to get authorization from the owner.

We would need to get authorization from the owner.

They gave slavers the authority to take back escaped slaves across free state lines. 

So, he then came back and went after her stating that "maybe I should file a complaint and contact the authorities because I cannot always drive to my back unit because there's a blowup pool there along with her kid's bikes all over the place.Any suggestions on how to deescalate the situation here?

The updated lease and housing authority documents were provided to us.

The great thing is that the daughter is on the mortgage so see if she will sign an undated authorizations allowing you to speak to the mortgage company or their representative about your plans as a family member who is taking over the property. 

Just make sure you have the authority in your Operating Agreement and you should be able to make these transactions.