I have used all the commonly Rx'd benzos and some of the barbiturates on/off since 2009. Point being: I have some experience in this area.
At day 12 the w/d from Ativan/lorazepam is over. Anything that is left is the psychological part, and as Kief Richards stated, that will wax&wane.
To stabilize at a new dose I would say 2 weeks is plenty of time (with a drug that has such a short half-life, and a short therapeutic effect).
How do you take your Ativan, btw? Do you just swallow it, or do you hold it under your tongue until it dissolves? (not a huge difference for most, some swear by the mouth technique..)
You stated you want your next drop to be 0.25mg instead of 0.5mg. That is fair, as you're on a "new" dose of the drug.
Suggestion: you could do 0.25mg drop for the next week and another 0.25mg for the following? Up to you.
- If you stated WHY you're on benzos, and this one in particular, I missed it.
I have never taken Zyprexa (tradename in US - dunno where you are). To the best of my understanding about this drug 5mg is a small-moderate dose. Your Psy gave it to you because it causes drowsiness, and I suppose could be helpful with anxiety, again - never taken it. It will likely be helpful with irrational thoughts, but aside from being drowsy I doubt it will help with Benzo w/d symptoms, as it doesn't hit GABA receptors.
Ps: you do not want to stay on anti-psycs if you don't have to. While it is a 2nd generation anti-psyc, it still often has nasty side effects (e.g. TD) **that come on with prolonged use** Other less severe side effects can occur much sooner, but don't discourage you from using it to help you off benzos.
Just a suggestion for when you get down to 0.25-0.5mg --> if you have ever taken Valium, and tolerated it well, it could be beneficial to switch to that. It is easier to taper off of, as the half-life is much longer, and thus the UP/DOWN benzo w/d symptoms aren't as present.
I went from taking this daily:
20mg Valium
2mg Ativan
1mg Xanax
1 - 1.5mg Klonopin
50-200mg Butalbital
(Rx'd for more than 1 reason, and, no, my doc is not a croaker

)
To:
15mg Valium
50mg Butalbital
Did this transition over a 3-4 month period. Everyone is different.
Point being....if I can do it, ya'll
likely can too!
Best of luck!