My $.02 (& I want change):
Don't do it. Figure out a way to keep her ... or you'll spend years regretting it. I've disposed of 2 cars in my life that I seriously wish I'd have talked myself into keeping - both were years ago & I still have regrets.
SPACE: Get a hitch try for some of the gear & free up the interior room. No solution to the carseat issue (unless you want to get creative and ditch the rear seat and hard mount the baby seat to the floor)
ENGINE: Good move on the Rotella to cure the oil consumption issue. Keep us posted on your results. The other thing you can try is to eliminate the PCV and replace it with either a breather or an oil catch can. That's what I'm doing on the Amigo & it looks promising.