I've been cursed with a pronounced babyface...the only really manly things I have are a prominent monobrow and some upper lip fuzz. When I smile I get two very caricature-ish chipmunk cheeks which make me feel horrible...and I fear that if I went on testosterone I'd just turn out a horrible child with a beard. So what I'm asking is, basically (I know everything depends on genetics but just as an average), the degree of baby fat elimination and sharpening of facial contours on testosterone. Thank you.

Your face will (minus bone structure) become as manly as it would have been if you had been born a dude.

or at least that is my understanding of the situation.

I think you'll be fine =]

I don't know how your face looks, so I can't make an assessment.

I really doubt you'd look like a child after, though.

I think you get some fat shifting away from the cheeks, because cheek fat is quite a female thing so the T might relieve your issue with your cheeks. 

I have the same issue, baby face/chubby cheeks and worse when I smile.

Iv always been called babyface, I remeber some girl cant remeber her name called me it as a nickname. she thought i was a guy and called me it cuz i was like a 19 year old that look 15, lol. And it botherd the hell out of me. Im now 22 and still get called it. But think about it. people that havent started T, its kinda like we havent started puberty, Its like we r 12.15 Most-(All) 19-22 years old (males) have deep voice, hair on there chin,ect. But normal people on the street think (well with me) that i am male, But not a 22 year old male but a 16 year old boy. I kind think of it as if im a late blomer. Once i start T (cant wait) thats when i am bcoming a man. Lol if u get me.

Also in the same boat here. I used to have serious chipmunk cheeks, but thankfully they've gone away slightly over the past three-ish years. But they're still more chipmunky than I'd like. I'm still hoping they'll slim out more on their own. Especially because right now I'm not sure when I'll get around to being able to do T. 

I think maybe age can be a factor for some peoples cheeks. Mine used to be far chubbier up to the age of about 17 or 18 than they are now aged 20 even without T and I still weigh about the same. Its just losing the 'puppy fat'. Most female faces lose fat over the years unless the person is overweight. T will very likely sort out the baby face to at least a passable amount.
I can think of one guy in particular who I know of who had an extremly round face and was quite slim preT and now his face looks more in proportion with his body after only about 3months on T.

i heard chewing alot of gum can help sink in the cheeks

Oh I've got the same deal. Losing weight in general will help, but you've got to lose a drastic amount before it becomes properly noticeable.