Hi [...],
[...] suggested I stop by.
You are overthinking it. Benzo withdrawal has so many variables, it makes no sense trying to plan the entire taper. Try not to live in the future, it stirs up anxiety.
Now, to your point, only 200 pills left. We can work on a taper which considers your pill problem.
But first to your questions. Everyone is different. You must answer those questions using your own body. I think the best way to do it is with a journal. Each day, record your taper, your symptoms, and any external stress. Week by week you can refer to your journal and modify your taper to have the fastest taper with tolerable symptoms.
Now to simplify your math by using the journal.
How about this. You start with your idea of reduction 0.038 mg per day but do it every day for a while. That is reasonable. If you do it everyday all the way to zero, you will be done in 132 days and it will only use 331 mg of your 400 mg supply.
Do not worry about percentages. Just do the 0.038 mg each day and do the journal. Then, study your journal and if you see a trend where your symptoms are getting worse, you can slow down your taper and re-compute to see if you still have enough of your supply.
How does that sound?