The new appraisal just doesn’t make sense, especially when compared to the first one.

Just make sure your personal use doesn’t exceed 14 days, or 10% of the rental days, to maintain its rental status for tax purposes. 

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 . 

It is my understanding that the new owner will have the house at the cost basis of my purchase price, for calculating capital gains taxes or depreciation.For gift tax purposes for you - FMV.For capital gain tax purposes for the recipient - your original basis/purchase price 

We're exploring creative ways to provide him with the cash needed for the down payment while avoiding triggering a taxable event.One strategy we're considering is purchasing his future primary residence ourselves, making the mortgage payments, and then, once we've built enough equity—comparable to the appraised value of his rental properties—transferring the title to him as a form of exchange.What are your thoughts on this approach?

LLC-A is a disregarded entity for tax purposes and I report the rental income/expense on Sch-E. 

I wrote the above for informational purposes.

What are the pros and cons of each, and which offers the least restrictions, flexibility and cost savings for my intended purposes?

  +100 acres of undeveloped land for the purpose of conservation, hunting, and timber harvesting. 

have looked into Batchleads as well but quality of data looks comparable  Check out traceestate.com $0.08 per individual and $0.15 per LLC.