The new search engine is rubbish for finding what you're looking for on the forum.
So not off the wall at all.
If you want your own policy not joint with your OH (of if OH doesn't drive / have a license) you may want to look at an insurance agent to find the best deal for you. A while back a thread came up with a poster saying their Insurance Agent in the UK found an insurer for them that was willing to give them a "no claims" record in the UK if her US insurer wrote a letter of recommendation / history for them.
I got added onto DH's insurance policy without a problem once I had my full UK license.
Additionally, if we return to the US to visit, will we be able to rent a car without being insured in the US? Would I have to drive on my US or UK driver's license?
You can rent a car, but you won't have any insurance on the car... (Unless your travel insurance policy covers rental cars.) You might want to look into taking out the rental company's insurance policy.
As for driving on your US / UK license you'll need to check with the company you book your rental car with as to what their policy is. Usually if you book through a UK booking agent (ie eBooker, Hertz etc) you will have to use your UK License for the booking to be valid and honoured (and same for a US bookings). But this will be stated in the fine print of your agreement. If you have both licenses you're covered either way.
Good luck!