I think you are puckering too much, which could be the source of the fuzzy buzz. Producing a smaller aperture is not a matter of puckering like a fish.

These are pictures of my aperture just after playing a note and pulling the horn off my lips. The picture with the bright light was just after playing C above the staff. The other middle might be after playing G above the staff or it could be a C in the staff.

Right after taking the horn off my lips, I’m sure the embouchure and aperture change because the mouthpiece holds the shape a little differently.