Jan
I think that is a wise decision. Decide what nadir you are comfortable dealing with and let that be your cutoff for a reduction. Is it TR? No. Is it SLGS? No (I'd probably take that out of your signature block and perhaps put "custom dosing"). But you have to take care of you as well.
There is nothing wrong with deciding what nadir you are comfortable with and what BG you feel you can comfortably shoot and then just adjusting his dose based on that. Sometimes we need to be flexible about all of this especially when our own health is involved.
Having said that, you do need to be aware that at any time on a good dose like this, he "could" drop below the nadir you are comfortable with. That's why SLGS uses 90. But even with SLGS, on a dose that gets him to 90, even if you reduce, the depot might take a bit of time to drain and you could still see a lower number the next cycle.
Remember...you can reduce at any time you think you need to. The protocol and the SLGS are just guidelines. Make it work for you.