An additional benefit of a detailed engineering-based Cost Segregation Study is that it can increase potential insurance premium savings as well as provide support for the property tax appeals process.

In your case, transferring the property from a revocable trust to an LLC where you and your wife are the owners should not affect the 1031 exchange, provided the LLC is a disregarded entity for tax purposes . 

The HOA (through the management manager) said OK, please provide a letter stating the door is the only way to make the unit ADA compliant, and I think it will be okay.A week later the developer presents a letter from an architect stating the door is the only way to make the unit compliant. 

I would find out who the manufacturer is and send it to them and confirm they will provide a warranty on this.

Gator most of the risk is on the person providing the earnest money.

Both @Nathan Gesner and @Lauren Stark have provided valuable insights on this.One potential path for you is to join an established team to gain experience.

Assuming this is a clean file, with no exceptions required, most Underwriters take anywhere from 48-72 hours to review a loan and get CTC, or provide further conditions. 

Is her goal to be nice and provide some of the gains or reduce her taxes by trying to split income between her and her ex?

Of those two, I actually like the first one better because you have a competitive advantage to that market and the amenities you could provide.

I just found out today that one of my tenants didn't pay rent and was sent a pay or quit notice but the notice provides them 30 days to pay or quit.