He cut out one piece of plastic relating to barometric pressure, and moved the taptic engine a bit. And all of this was on the 7, so Apple surely had space for a headphone jack on the 7+, right?

Maybe wired headphones are going the way of the DVD drive. But at this point, the change has felt very user-hostile. If they cared about their customers, iPhones would support USB-C and wired headphones.

> so Apple surely had space for a headphone jack on the 7+, right

That’s easily answerable by heading over to iFixIt. You’ll see the Plus models are near identical to the non-Plus in available space, just the Plus has a bigger battery and even more circuitry (do to the dual camera). Apple doesn’t waste any space inside their devices typically.