Hi jv, Let me try to shift your thinking a bit. I will answer your question about how bad it can get, well for me anyway, in a bit.
Instead of asking how bad it can get, why not try asking how good things can be? I sleep a full, restful 8 hours a night now. I wake up feeling well, no hangover, no shakes or anxiety, no upset stomach, no vomiting, no headache. I do not have to reach for a bottle when I wake up anymore; choking down a few slugs of booze to calm the horrendous shaking and blind horror of facing yet another day. I remember the night before and the things I remember are actually generally good things! I don't have to worry if I have enough booze around to last through the night. I do things, fun things with my friends and family. I have peace. Heck, I just landed a job today. I could go on and on. It really does get better, physically, mentally, and emotionally.
So, how bad can it get? Well, I didn't drink as much as you are but it did become every day around the clock. Physically, I was a mess. Hospitalized 7 or 8 times in an 18 month period, detoxes that got worse and worse, shaking so badly I could not get a vodka bottle to my lips. Once, I actually poured some on the kitchen counter and lapped it up like a dog. Nice, huh? Let's see; two DUIs, spending a few days in jail, losing two very well paying jobs, one of which I held for 16 years. Seeing how scared and crushed my wife, son, parents and sisters were. Being told by many doctors that I was dying. Drinking two bottles of vanilla extract the night I got home from a detox because I was still shaking. Cutting my wrist while in a blackout. My wife committed me at the psych ward but I convinced them to let me go. I started drinking again as soon as I got home.
So, yeah, it can get pretty bad. But when you decide to stop, decide you don't want that crap anymore, it can get pretty damn good.