I'm a coloratura soprano, and my college tends to focus more on operatic repertoire which I have ZERO experience in. Most of my problem comes from admittedly terrible breath support, singing alto II in concert choir/my college's a capella ensemble and therefore not getting the chance to develop my upper range/singing very low in my range, and (according to my voice teacher) the fact that I have a very deep, throaty speaking voice.

Nothing my voice teacher (a mezzo) is telling me to do to bring my sound more forward really helps (such as speaking my entire piece in a nasally, squeaky voice) and she's always saying how "weird" my voice is and she has no idea how to fix my resonance. It's been suggested that I switch to the only other vocal teacher (who is a tenor and would have a better idea of how my voice works), but I'd like to avoid that.

Do any of you have any tips to bring the resonance forward or training yourself to breathe properly?

Your voice placement should be at the front of the mouth, the further back it is the less it's going to project and the more nasally it will sound. that, diaphragmatic breathing and work on your vocal projection and you should be set.
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Huh, I have found that moving the air direction from forward to farther back has helped tremendously with tone and strain.

I lift the soft pallet as much as possible, support well and aim the flow directly out the top of my head. This seems to be about the area where the soft pallet ends and the hard pallet takes over.

To each their own, but moving the sound further forward just sounded bad and caused me to inadvertently strain. Now, both high and low notes (in my range) are much more effortless.