Bruce, in reading your post carefully it appears that you're looking for something that's easier for your wife to get into. That pretty much rules out another full size SUV or pickup. There's lots of guys on here who think you need a full size pickup to tow anything with wheels on it. Your weights you estimated are likely to be spot-on, your trailer's GVWR is a shade under 4000. Basically a smaller ultralight, certainly not needing a full size pickup. I used to tow a larger ultralight than yours with a Ford Aerostar, and it towed pretty well despite having much less power than today's vehicles.
I think the Ford Flex or similar mid size SUV you mentioned might work well if you're careful about what you pick. Forget about FWD, AWD is the way to go. You also need to make sure that whatever vehicle you pick has adequate payload, a factory tow package, and a receiver that can be used with a weight distribution hitch (not all can). Get one with a real transmission- not a CVT. Get the most powerful engine in whatever vehicle you pick- the 2.7 Ecoboost available in the Flex is also used in the F150 and would have the power to tow your trailer easily. Don't look for any improvement on towing mileage though, it's going to suck unless you use something that burns diesel. Then it will just suck less.