That's enough jacket for the two of you. That's similar to what my HWM fit. I knew it was off the moment I tried it on.
IMO, Fully cinched, correctly sized, this jacket should literally be skintight. That's the whole point of the side adjusters. Uncinched, you should have about 3" - 4" of space. If there's still room left over even warmest of layers you have, the jacket is too wide.
You're a slim dude, this isn't a jacket you should be wearing. Send it back for a remake. There's no way they'll say "Oh, it's supposed to look like that".
Yep, any maker who stands behind his product should see these pics and say "Sorry we got it wrong, let's remake it."
Edit: but i think you should stop wearing it asap so that they still get a "new" jacket returned to them.