Title - Lender's title insurance $600 --> Do I have to pay this at closing?

Yes, your interest rate will be lower, but the Mortgage Insurance Premium (not PMI as many people often call it) is not only a burden, but a huge waste of money (basically paying the FHA's bills).

Insurance could run me about $80/ month or so. 

For now, you protect yourself with umbrella insurance.

Include a provision about paying taxes, insurance, repairs, etc. to become part of the balance.

Then they are responsible for upgrades, repairs, taxes, and insurance. 

I recommend talking with an insurance broker/risk manager that currently doesn't insure you to tell you the amount of risk you undertake with a pool.

I’d call your insurer first about this

Make sure you have a title search done and get title insurance.

@Matt Matyas To have an actionable plan that will work in your area, you'll need to speak with the Town/county board of health and/or a reputable septic installer/maintainer.