In San Diego at the current rates for a purchase loan (which has better rates than an ADU additions) at high LTV, I show 1% does not cash flow on a sustained basis.  

Raising your credit score will get you far better rates personally as well as with private lenders for your LLC. 

Even at a high cap rate you've got several million dollars of market value here, so I'm curious about your base numbers.

No - absolute max for DSCR is 85% LTV and that is extremely rare and typically not workable in this rate environment anyways.Standard/common max is 80% (acquisition and rate-term refinances) and 75% Cash-Out Refis

Charge the tenants a higher rent rate and include utilities with their rent.

We own our house in Seattle and are trying to determine the best strategy for our move - what approach would net us the most money over the next 1-3 years.

I’m the last person who should complain about grammar, but these are yellow flags, at best.

You start by mentioning your age... you'd need everything to go just right for the rest of your life to make, best case, $400 or less additional each month net cash flow. 

At the same time depreciation recapture is taxed at regular tax rates, not capital gain rate.

There are also case by case opportunities within the North Phoenix market where rental rates are stronger.