24mg is the ceiling dose curently accepted in addiction medicine. It is a lot. However, FOR NOW, maybe stay at that dose for a couple of months and get to a stable point. If you feel like taking less, take less. Don't use it to chip. If you were truly using 100 grams of heroin in a 2 day span... I'd put you on a high as fuck dose too. Frankly, unless it was seriously stepped on and your tolerance is through the roof... I would find it hard to believe, but there was a time when I was moving drugs and using a large amount of what would become tar heroin. My tolerance was fucking huge and I had been using for a long ass time. My first doctor put me on 8mg and quickly stepped it to 4mg.
Let me tell you that the 8mg did enough to not make me sick but gave me cravings like a motherfucker. After a year of chipping and that doc being hella inconsistent I found a clinic who told me to be straight up with them. I was... I said that when I wasn't using Bupe I could shoot a gram of cleaned up, micron filtered heroin. That was the truth. My doctor put me on 20mg of Subutex. That dose literally saved my life. The doc also made me take in front of her for a week and talked to me for an hour about why and what and all that stuff. So that doctor probably saved my life. I stayed on 20mg for... about 3 months and gradually brought it down to 8. Stockpiled the pills for a rainy day. Turns out most clinics aren't as cool as that one. When I moved away, I used that stockpile and tapered down. It saved me from relapse and it has allowed me to say "Yeah, I'm clean." for the better part of 10 years now.
It is a lot. I'm surprised that they're prescribing a benzo with it. The doc's wanting to step it down, makes 100% sense. Frankly, if you see two docs: one for addiction and one for your "other mental shit". That would probably be good. Address it on two fronts. Maybe toss in a therapist and some group meetings while you're at it.