I want to mew, but I feel like I can't even close my mouth all the way.

1. How close together can you get your teeth, without the bottom tooth getting in the way?

2. Is it just this one tooth that sticks out, or do you have crowding in general?

I tend to think that teeth lightly together and teeth slightly apart are both acceptable, though one of those may be preferable according to the nature of your CFD (craniofacial dystrophy). So, if you can at least get your teeth close together, and seal your lips, it's a significant improvement from slacking your jaw. If you succeed in achieving palatal expansion through a good tongue posture, there's a chance that your protruding tooth will move back in a little, due to having more space. A good lip seal should help with that as well, but remember that there's no guarantees here.

If this tooth prevents you from getting your jaws close together, and you can't achieve a good lip seal at all, then perhaps look into appliances or visit an orthodontist who understands the harm of extractions and treats without them (search keywords: "functional orthodontist, myofascial orthodontist").