2) What protective measures should I consider as a buyer in a seller-financed deal to ensure the offer is as efficient as possible?

Here are some specific questions I have, but any additional information is welcome:Safety and Community Feel: How do locals view the safety and overall community vibe in Pine Hills?

If it’s a safety issue, I’ll of course make sure the premises are as safe as they were before any required maintenance was done, but she is now suggesting that if I don’t reimburse her for those specific anchors, I am violating fair housing laws for familial status and/or tenants rights regarding not incurring costs for required repairs.

It's an effective temporary measure to buy a small amount of time to figure things out but its like poisoning the well, it will have long lasting effect on your personal credit and dismissing the BK won't change the credit impact.If you are doubting the validity of the lady's claim to the property, file a quiet title action and have her prove it belongs to her.

A landlord does not need to provide a reasonable accommodation for an emotional support animal when:The property is an owner-occupied building with four or fewer unitsThe property is a single-family home sold or rented by the owner without the use of an agentThe emotional support animal poses a risk to the health or safety of other people, or a risk of substantial damage to property (but this risk must be specific to the animal and cannot be based solely on assumptions about the animal’s breed)"Definitely have a chat with a local attorney to ensure your local laws apply, nonetheless since its an owner occupant, it sounds like you have some recourse to deny this request. 

Ultimately I am worried about protecting our business's reputation, the safety of our tenants, and having a viable rental. 

Now a landlord (and architect), I wouldn't build out the space without the second stair since it really is a safety issue/liability (especially in case of a fire) if anything were to happen.Full excerpt of building code below:According to the Chicago building code on egress requirements, the third story above grade plane within a dwelling unit [which in this case is the duplex-up unit], all the following conditions must be met:1.) the building is equipped throughout with an automatic sprinkler system2.) the floor area of the story does not exceed 1600 sq ft3.) the dwelling unit has an exit that discharges directly to the exterior at the level of exit discharge.Your third story attic space is unlikely to exceed 1600 sq ft, but you'll probably find the sprinkler system to be cost-prohibitive.

Obviously I can picture it, but I don't know the exact measurements. 

Haven't we learned anything with the measures taken during the pandemic?

Let's put away the high school dick measuring sticks and stick to what matters-- you being successful.