I'm trying to determine which *A FF scheme to join, but I'm also open to joining a Skyteam or Oneworld FF scheme if you guys think it would be a better fit.

Thanks in advance and I look forward to hearing what you guys have to say.

To answer the questions from the initial post:
(1) What is your home airport?
Currently, it's OSL. However, we're considering moving to Singapore, so then it would be SIN. For the rest of this post, I'll assume we're moving to Singapore as that seems most likely.

(2) What types of fares do you usually buy ? (C, F, Y, etc.)
I usually buy the cheapest economy fares I can find that fit with my schedule.

(3) How many miles do you usually fly each year? (<25K, 25k-50k, >50k)
On average, somewhere between 15K and 25K, but that will likely bump up to 25K to 35K.

(4) Do you have any kind of status at present? What is it? (UA Premier, M&M Senator etc)
No, but I have approximately 40,000 United Mileage Plus miles

(5) What is most important to you in a FFP? (Frequent upgrades on travel, priority services when flying the airline, good award redemption rates, free lounge access, etc.)
Upgrades on travel and lounge access are the most important to me.

(6) Which routes do you fly most often (US Domestic, Transpacific etc)
Our family consists of an American (me) from the southeast, a Norwegian (my wife), and our son. As a result, we will fly at least once a year from SIN to the southeast (either ATL or SAV) and from SIN to OSL. Outside of those two yearly trips, most of our travel will likely be long weekend type getaways within Asia.

(7) Preferred Airlines
I don't have any strong preferences.

(8) Do you travel for work or pleasure? (Can you chooose your airlines, class of service?)
Currently, almost all of our traveling is for pleasure, but it would not be completely unexpected to have some work related travel as well. We can choose airlines and class of service.