Maybe smooth out the edges now, adding bits of foam here and there to smooth up the cheeks and whatnot. And I just used foam for the teeth and glued fabric over those, since it's lightweight and the same material as the head
Don't use cardboard for any part of the head; it will get soggy, even if it's the teeth and they're covered up, and they can grow mold, which is very bad for your health.
I just lined the inside with black felt and sewed a tongue with two pieces of fleece.
A thing for ears could be to put up a pace of foam uncut, and trace where the ears should go while its on the head, with the ear curve and whatnot. I saw a tutorial online, just search ear for fursuits
Mot suits I've seen don't have a chin, since most animals don't have one
It's just the neck right after the head ends.
It looks great so far though!!