Skip tracing and texting/calling a somewhat generic list with poor skip trace data is the perfect recipe for the results you've experienced so far.Since I got started as an investor I learned really fast that paying a premium for the best skip trace data available was worth it.  

At the time, I was able to work with an insurance agent to get a specialized policy for vacant homes (I was rehabbing it) for a premium of $1,975.Late March, I received a renewal with the premium $2,827, for a vacant home (now tenant occupied).

Investors are not going to pay the same premium that an owner user would.

However, two things that I observed - 1) the turnkey company I am working with has shared a proforma that has ~10% to 15% premium price compared to similar properties sold in the area. 2) they have a contract in place before the inspection and appraisal.

Second, I received a request from State Farm today: Please provide the gross sales/receipts amount for the insured location(s) as reflected on their most recently completed tax filing or anticipated gross sales for the upcoming fiscal year.This strikes me as a little weird and perhaps I shouldn't jump to the conclusion that this info will be used against us (and result in a higher premium).

Find new developments and buy their demo homes or premium lots.  

Essentially, this single fact is where any premium is derived for the price of the property. 

More than double the current policy premium.

Is there a Zillow premium or something that get's you more exposure?

At least your insurance premiums will be much cheaper on a new construct versus an older existing house.