It is true that the Dream is not up to full speed, it has been lacking one diesel engine since late June, and they have been trying to repair it while the Dream has remianed in service. So ports that require full speed cannot be reached in the alloted time. Instead of having a four port itinerary, the Dream will probably only visit three ports in a week until the engine is repaired.
It is normal not to have a specific assignment more than two months from your cruise, while having a guarantee category of cabin reserved. Assignments are usually made immediately after the final payment date, which usually occurs two months prior to your cruise. So for a Christmas cruise, the final payment date should be in late October. Also, you'd probably will not know which flight until you receive your cruise papers. You get your cruise papers via the mail, or by e-mail, about a month before your cruise, at the earliest.
So be patient. Talk with your travel agent regularly.
Although the Dream has been slowed down, recent cruisers have reported that the staff is working overtime to please you, knowing that the ship has been letting cruisers down. Enjoy the ship, roll with the disappointments, and have a great time on your cruise. Not every cruise is perfect, there's always some disappointments and great things that happen on one. Don't let the little disappointments ruin your cruise.