Wow, all questions are answered already...
One that remains: empty or not?
Very often the bulb is part of the forepeak ballast tank. As it's so far forward, you need less ballast to correct the trim.
But I can tell you, it's a special experience crawling around in the bulbous bow with the usual 10 cm drab all over the place. Even the disposable head-to-toe boiler suits don't keep all the mud out.
On ice breakers: newer models have an ice-breaking stern. They go stern-first when breaking ice. This helps as their azi-pods suck the water out from under the ice. When the ships weight then slides on top, it's easier to break the ice. I guess for light ice, they just go bow first.
I've seen them in action. There is hardly a more impressive sight. In northern Finland you can take "ice-breaker cruises" for those interested in experiencing it. Included in the trip is a swim in a survival suit amidst the ice blocks.
Bruno