first of all depression can cause us to be irritable. it sounds like it's "coming out sideways" towards your hubby. are u getting help for your depression?
you mentioned "He doesn't need me in the same way I need him. He doesn't know what it's like to feel this deeply." how does one know what others feel? how deeply do you feel?

your post-"Bitterness?? Oh my, where would I begin? I guess that is mixed up with the sadness and anger and hurt inside that hole in my heart."
what causes you to have these feelings? sadness, anger, etc. perhaps that would help us know more about you so we can relate to you our own experiences and ways we overcame them.

"The thing is, I don't LIKE feeling so mean to him, and I actually DO think I would feel better if I said and did nice things for him. But for some reason I just can't let this bitterness go.."
why not try to be kinder to him instead if you do feel being nicer to him would make you feel better about yourself?

"I just can't let this bitterness go" but you can let it go. we have free will. we are what we choose to be...
i'm not trying to bust you...i felt somewhat as you do years ago and i was a mad, angry,hurt person. i didn't like being in my own skin. i didn't like myself, so my solution was learning tools to rearrange my perception of my life and the ppl i valued in my life. i went to an excelent therapist that opened up my eyes and helped me to metamorph myself. he guided me, i did the work. painful at times but well worth it. i hope you can find some help in my post or perhaps give you "food for thought".
ps my signature by ayn rand may help you to have hope.
pss your alcohol abuse is thwarting your efforts too hayward, imho. it is masking your problems.