I think you are misreading the data sheet (your attachment can't be opened, BTW).
I've been using the BNO055 for quite a while and am pretty familiar with the data sheet, but after reading some more (my data sheet version is DS000_14), it is not at all clear to me that you can do what you are hoping to do and then run the device in fusion mode.
Assuming that it IS possible to have different accelerometer settings in fusion mode, have you been able to find a statement of what those restricted settings might be?
I haven't, and my reading of page 28 of the data sheet indicates that those settings are "auto controlled" in fusion mode, and are NOT configurable by the user.
You still have not said what you are trying to do. If you just want to read raw accelerations, don't use fusion mode, and then you can use any range you want.