At least up here, service is VERY important and VERY complicated, so you and/or your attorney need to make sure that you cover all the bases. 

Property tax is a very local issue, and the details of particular problems can vary widely based on the statutes in that state.I'm mostly wondering what issues people have run into , and if they've hired outside help to deal with those issues.

My primary goal is to find a legal partner who is responsive, reliable, and thorough, ensuring that all parties are kept in the loop and that closing can proceed smoothly without last-minute surprises or delays.I'm reaching out to this knowledgeable community for advice:Have you worked with law firms not based in the state where you were purchasing property, and if so, how was your experience?

You can "split" the properties and determine the value based on a formula of your choosing.

I wouldn't necessarily be uncomfortable with that (I would actually be so proud haha) since coops are community-based complexes so their primarily reason for checking the background and financials is to make sure all their neighbors are in a good standing. 

You may also refinance based on the new appraised value with 90 days seasoning at 75% LTV.

If you can definitively prove that the seller intended to deceive you about the square footage for their personal gain, you may be able to take legal action, but probably low chance of success considering you had ample opportunity to measure the home or get an appraisal with measurements prior to closing, and had your chance to negotiate the price based on square footage and all other factors prior to closing. 

I am based out of Phoenix and plan to work here.

I use a filtering system based on the house number and street so every email for a particular transaction skips my inbox and goes in to a specific labeled folder.

Study different exit strategies, choose one based of off your goals, timeline, and risk tolerance, then find a mentor.