One your loans will be a higher interest rate, next you will have annual filings, the cost of a registered agent every year, and items like that. 

Refinanced August 2020 into a 15 year loan at 3.375%

If a HELOC isn't an option due to Texas laws, you could consider a cash-out refinance with another property or a portfolio loan, even if you want to keep your current rate.

I didn't see a need for a holding company but if someone wants one, you can just use another LLC as the holding company.

I use a loan servicer who processes the borrowers payment and then sends to me.

Did you close this with a hard money loan?

Usually when I close on a house, the insurance company sends out somebody to do a visual inspection.

Total profit less closing costs and commissions will be about 42,500 each or 85k total.I would for sure get a construction loan, may be worth approaching 2 or 3 different banks and getting separate construction loans from different banks. 

Since agency loans don't allow you to put the loan in an LLC, ask your wife this. 

Yes, just like you claim depreciation on the use of your property, any company including an insurance company claim depreciation when they pay for your damage.