I use back button focussing on my D750, use single point focus (the central point) and am able to recompose as described and fire the shutter, but I do keep the back button pressed. My D3200 works the same way.
Same here, it's a bit annoying to first have to convert them. Do you guys convert to DNG or TIFF? I'm using DNG at the moment but am not sure the beta conversion is clean.