Leverage SBA (owner occupied at 51%+) for the construction of just the Office piece.b. 

The short answer is that much of the rental market is moving to the "surplus" market.

They don’t always post a flashy “Upcoming Auctions” banner, but check the “News” or “Public Notices” sections—sometimes surplus or impound auctions (like vehicles) get announced there.

The commercial office space is owned by my LLC.

This particular policy originally included three properties, and I successfully found coverage for the other two.Are there any surplus lines carriers you’d recommend?

Sadly, this price-gouging behavior has become the unfortunate new norm in the insurance industry.There's a high likelihood you'll need a broker familiar with surplus lines.  3 weeks isn't much time - if you aren't working with someone already you need to get in touch with someone asap.

As far as home office no longer being an IRS "red flag" I guaranty that if you put a home office deduction on a personal return on Turbo Tax it will move their audit risk needle.

Has anyone invested with the Ian Djuric at the Blake Capital Group (https://blakecapitalgroup.com/) formerly Djuric Family Office (http://djuricfamilyoffice.com/)?

Fair points, this definitely depends on the power company's policy on surplus generation.

This is a mixed-use property with retail, office, commercial, residential, and hospitality use.