Just got home from 10 day Dawn Baltic cruise.
In general, we had a good time. I will answer some of your questions:
1. Free at Sea Plus - We opted out because we had 1 sea day and the itinerary was port extensive. Having said that, you should be aware that a 7am to 9pm port day will not mean 14 hours of free time. On Board time is anywhere from 30 minutes to an hour before the ship leaves. I did not feel any need to do the Free at Sea Plus upgrade. We did additional upgraded dining, but the alcohol selection with the regular Free at Sea was good enough. The internet is not good and the Plus internet will not be much better. Opt in to your cellular network provider for international wifi or get a Wifi egg.
2. Ports in Europe - I don't know what ports you are traveling to, but most of the ports we were at were not really the "find a bar and relax" types of ports. They were heavily industrial ports and you really need to book shuttles or exclusion transportation to get to the cities. We NEVER book excusrions through Royal Carribean or Carnival, but we really enjoyed the "on you own" excursions through NCL.
3. Cabin - we opted for a Family Suite. It was big enough for 4 of us and had just the right amount of amenities. A big Bath Tub was a huge selling point. You will feel the ship move no matter where your cabin is. Dawn is a small ship.
4. NCL Airfare - Booking Airfare through NCL will not allow you more than 2 days in the cities of embarkation and debarkation. We opted out so that we could stay in Oslo 4 days and London 5 days. It ended up being cheaper.
Overall, the Dawn is a small and capable ship. The free dining was subpar, except for Osheehans. The paid dining was excellent. The service was great as a Suite Guest. If you find the right bartender, you will not miss the top shelf stuff. My fav bartender was heavy handed in pouring and often times gave me upgrades.