I stayed with my wife and two small children in the Fort Wilderness cabins twice for 5 nights in January 2005 and for 8 nights in January 2006. We all love the cabins and Fort Wilderness.
You asked if the cabins seem small and dark. The cabins are small, but of sufficient size. The biggest drawback in terms of size is the lack of storage space. However, my wife and I love having a bedroom separate from the rest of the accommodations so the kids can go to sleep early and we can stay up. We also love the full kitchen with full-sized fridge, stove, microwave, dishwasher and sink.
In terms of darkness, the lighting in the cabins is dim, except for maybe the immediate kitchen area, which has good lighting. I have commented to my wife that we should go to a local shop to buy a lamp for the cabin whenever we stay there.
There are four beds: two twins as part of a bunk bed in the bedroom, a double bed in the bedroom. And a double-bed that pulls down from the living room wall.
There is a parking spot adjacent to each cabin.
I did not notice many bugs in Fort Wilderness.
It is a long walk to most of the amenities, though if you don't rent an electric cart or a bike, there is the internal Fort Wilderness bus service.
Of the two main pools in Fort Wilderness, I have only been to the pool near the Meadow Trading Post area (the pool is also right next to the campfire/outdoor movie area). Before I saw this pool I had low expectations of the pool area being a 1970s concrete jungle with no theme (based on Disboard posts from other people), but when I went to swim there I was pleasantly surprised. There is no big slide and there is no extra theming, but the pool is very large and the surrounding trees and campground landscape make for a nice view around the pool. There is also a childrens wading pool next to the large main pool.
There is another pool near cabin loops 2500 and 2600, but I did not visit that pool. I had rented an electric cart from Disney for $40 a day (this includes the 10% discount for renting at least a week), and so it was very easy to get to the larger main pool behind the Meadows Trading Post. Our whole family loves to ride around in the open-air electric carts (there is a windshield).
Another big plus is the boat to the Magic Kingdom from the Ft. Wilderness marina.
We are not a family of campers, but we love Fort Wilderness, the cabins, the campfire program, the outdoor movie, the Trading Posts, the quiet, the trees, and the Disney magic.
I have been to Disney World thirteen times, and our January 2006 trip, which was spent mostly in the cabins, was the best vacation I ever had, and some of the best days of my entire life.