I'm about your father's age. Getting insurance two years ago wasn't easy due to my age, but we were able to get Swiss Medical through our daughter as family members. There aren't many options for new accounts once you hit 65 as far as I know.
I dropped Medicare before leaving the U.S., which saved some money. Good thing, because my current Swiss Medical bill (for wife and myself) was $590k. We have the highest tier, but dropping down wouldn't save much, especially as I have several serious health issues.
Prices and exchange rates change, but our dollar cost has actually been fairly stable in the 2 years since we've been back, about $460/mo.
Hope this helps you.