4.) The $15 fee for bringing wine/champagne on board - is it per bottle, or total no matter how many bottles you bring on?
The $15.00 is a corkage fee if you take the bottle to the dining room. There is no charge for bringing the wine/champagne on board the ship and drink it in your cabin.
5.) I'm worried about the dress code. I almost ALWAYS wore sandles on carnival except at dinner. Are t-shirts, shorts, sandles, and pool wear acceptable when going from one location to another? Meaning, can I go from the pool to another part of the ship without getting odd looks during normal pool hours?
Sandals are perfectly fine, in fact you will find most people either in sandals, flip flops or runners during the day and also wearing shorts and t-shirts. If you are in swim wear, they ask that you put on a cover up when you go from the pool to the inside of the ship. Mind you I've seen a few people walk into the Lido to get their lunch, etc., in their bathing suits and nothing on their feet - YUCK when I have to look at some guy with a bare belly as I am getting my food.
7.) Any idea how much laundry service is? I was hoping to pack a small amount of clothes and then do a wash on board myself, but apparently I can't on the Oosterdam. If it's reasonably priced, I might still pack light for the 7 day voyage.
They usually have a special on laundry - there is a blue laundry bag in the cupboard where the safe is and you can put all you can get into it for around $15.00. They do a great job!
Can't help you with your other questions, but I am sure someone on the board can.
Have a great time!