I may have relevant experience:
My Daily driver is a 2016 Fusion Energi (PHEV). It's the nicest vehicle I've owned, and has given me 0 problems in the time I've owned it but it's still pretty new. I've put about 15k miles on it and dragged the lifetime fuel economy from mid 40s when I bought it to 86.6 mpg at hte end of this summer. I'm 6'1", wife is 5'10", and we have a rear facing baby seat and a Mastiff in the back seat with nobody being uncomfortable (except maybe the Mastiff on longer drives). It has no problem with 4 adults either, although 4 adults + luggage or something would be an issue due to the lack of trunk space.
My wife has a 2013 Santa Fe (full size, three row, V6, AWD) and is typically in the 24-25mpg range. Might get more favorable trade terms from a Hyundai dealer, and could get you in a slightly larger, more capable and fuel efficient vehicle that you're otherwise very familiar with. It's had a fuel injector and rear driveline coupler replaced under warranty but has been a good vehicle thus far.
Honestly, nothing is worth signing up for negative equity. That just means you're financing debt and digging an even deeper hole for yourself. I'd stick it out with what you've got, or try to sell the current vehicle privately to get more than what the dealer was offering for your trade. It might also be worth stopping some place like Carmax to see what they'd offer for your trade.