Email and website are optional. They are only so a signature can be linked back to you later, they do not show on the public wall now, and they are never shared.
It reached its limit of 100 signatures. Nothing more can be added, which was always the arrangement.
No signatures yet. Yours would be the first.
Signatures are held for review before they appear, and stored as pen strokes drawn into vector paths, not images, so they stay sharp at any size and take their color from the page.