I guess, you need to decide first, if you prefer to use the two different expression pedal functions within your BOSS pedal to control two different controllers within the PROFILER e.g. Volume and Wah. Or if you just use one of those expression pedal tapers and set it up as a Wah Pedal and then link the Volume Pedal function to it selecting the WahPedal to Volume option. Don't mix and confuse those two approaches.
I read comments, that the taper of that BOSS pedal doesn't respond evenly and can come in late. Perhaps a limitation of that pedal. Try to change polarity at the pedal. That polarity selection and the Pedal Type you chose within the PROFILER settings should match. Otherwise the response curve might be suboptimal. Also make sure, that the range pot at the pedal is set to maximum. And calibrate the pedal.
If you use WahPedal to Volume, the pedal maintains the latest Volume Pedal level, when you activate a wah effect or load another Rig with an active wah effect. That is intended behavior. So you need to organize your soiunds accordingly. Or you use two seperate pedals, one for volume, the other for wah. That's what I do: I have one dedicated pedal for volume, which I can use at any time. And I have a second pedal fro wah and pedal pitch effects as well as Morphing.