Hi!
i've decided to answer your questions.
1) No, they could not have opened the compartments, let the ship flood evenly and therefore keep it from breaking apart. The hull of the ship is designed in such a way to displace a large volume of water. This is because the buoyant force is equal to the amount of water displaced by an object. The more water displaced, the greater the buoyant force. If they had let all of the compartments be filled, the weight of the ship would be more than the water displaced by it. Therefore, the buoyant force wouldn't be able to keep it afloat. The ship would have sank.
2) I’m not sure if you meant stop the leaks from the inside or the outside so I’ll answer both ways. They certainly could not have pushes furniture against the leaks to stop them from the inside. In your experiment, a small hole does not allow much water to enter per second. The Titanic, on the other hand, was taking on 700 tons of water per second. No mattress of furniture would stop that water or even slow it from entering the boat. As for the outside, the leaks were on the Starburg side under water. A mattress would have floated in the water and the furniture would have sank before anyone could get the furniture to the leaks. Besides, the people pushing the furniture against the leaks would have been sucked in too because the leaks were so large that a piece of furniture wasn’t going to cover it.
I hope that helped! Let me know if you’re curious about anything else.