If either of these were addressed in the agreement, send/deliver a notice of violation per local law and the terms of the agreement.The lease states “ Tenant shall not allow any other person, other than Tenant’s immediate family or transient relatives and friends who are guests of Tenant, to use or occupy the Premises without first obtaining Landlord’s written consent to such use.” 

The deed of trust securing the Note will provide for the following: (1) PROPERTY TRANSFERS: (check one box only) (a) Consent Not Required: The Property may be sold, conveyed or leased without the consent of Seller, provided any subsequent buyer assumes the Note. (b) Consent Required: If all or any part of the Property is sold, conveyed, leased for a period longer than 3 years, leased with an option to purchase, or otherwise sold (including any contract for deed), without Seller's prior written consent, which consent may be withheld in Seller's sole discretion, Seller may declare the balance of the Note Initialed for identification by Buyer and SellerTREC NO. 26-7 Seller Financing Addendum ConcerningPage 2 of 2 11-2-2015 (Address of Property)to be immediately due and payable.

For contractor #2 - work up a document that states he's not to proceed with any more repairs without your written consent and have him sign it.

I plan to write up an addendum to the tenant's lease confirming that the boyfriend has been approved by landlord as a long-term guest of the tenant, with legal responsibility to follow all the rules as outlined in the lease, but with no right to occupancy without consent of tenant or beyond the terms of the lease (runs through December). 

A couple of weeks later, I got a message from Airbnb attempting to get my consent to issue her the full refund "before they start a process". 

However, the lender has the option of calling the note if a transfer takes place without his consent.

I am not a lawyer and thus am not sure if it is illegal to run a background check without your consent. 

You can run a criminal check after, with consent.

Tenant agrees that no painting shall be done on or about the property without the prior written consent of the Landlord."

Does the contract allow the contractor to perform work “outside the scope of the agreement” without your written consent?