you could try using more air, and getting a firmer grip on your mouth piece, you might not be taking enough mouth piece in either, you could trying taking some more of that. Those are always the things we try working with when we're having trouble playing in our bass clarinet section, and if none of that works try talking to your instructor and they're no help just play it out and hope for the best, sometimes you may hate what you're playing but it sounds awesome from the audience. I hope this was helpful!

Thanks
I've tried using more mouthpiece, pushing the reed up farther, putting it lower, blowing harder, angling the instrument differently....It just doesn't work. :/ But I'm just going to practice as much as I can.
Hah.

Have you tried a mouthpiece patch ?

May help with the teeth vibrating by providing some padding.

Or try a different mouthpiece.

Could be the instrument has a leak or few.
How long since its been serviced ?

i agree^, mouthpeice patches are great.

for the airy sound, it could be too stiff a reed, i think you said you use a 3, try a 2 and a half maybe?

for the spitty sound, my first guess would be too much spit (gasp?) try sucking it out of the reed before you play? although if it's a consistant spitty sound even when you first start playing, that's odd.

solas ane is a great peice :D

I really have nothing to say about how to help i just wanted to add that Bass Clarinet + Flute/Piccolo Duets are AMAZING!