The market tells you it's a garbage area. In Napa Valley, there are 3 waterfront neighborhoods, Riverpark, Yacht Club & Milton. The average sales price of the prior 3 sales are; Yacht Club $1,278,333, Riverpark $1,101,667 then Milton $672,300. If that news isn't bad enough the last sale on Milton was in May of 2019. So the market is telling you this is a dismal location to invest.
I don't understand your 2nd question. I would not invest a nickel in the property I would sell it as-is and invest the money in a better area with much better cash flow.
The 1% rule comes from my 25 years of experience as a very successful real estate investor. If you are running a long term rental it MUST generate a minimum 1% of the value in gross cash flow each month or you are losing money and you will go out of business. Additionally, the market says you can get greater than a 1% gross cash flow monthly so why would you subsidize a tenant's living situation with your hard-earned money?