Used to, but I try to think of the walk to and from the bathroom as time to stretch, and I don't take me phone to the bathroom so I don't bring distractions back to my workspace
Well, everyone has to use the bathroom. But I recommend going to the bathroom before the work session if possible, so that you don't have to pause. If you do end up taking a break, pause the timer so you don't count break time as working.
I haven't thought about it. I guess it is a disruption especially if it's done in the middle of deep work. I think it would be beneficial to go before deep work, in order to maximize your time spent doing deep work. It's hard to start deeo work up again once you've stopped. Mainly this is due to the disruption in work flow. Your train of thought is broken, hence you have to take time to repair (refocus), which is an unfortunate delay.