I guess I'm qualified to answer these questions.

There are a couple of things with scoring.
1)
You receive points for your society (social, economic, research, military) each turn and the final state of your empire is unimportant. You receive diminishing points for your total society the further into the game you are. By this I mean that the same ship is worth more, pointswise in game year zero than in game year five. This makes sense as a fully loaded BHE in year one is a much more impressive feat than a fully loaded BHE in year ten. This does mean that if you can get a fully developed society very early in the game you can score massive points for those early years because you have achieved an unexpectedly strong level of domination. As you go deeper into the game, the potential number of points you can receive diminishes as a fully developed society is simply worth fewer points at that point and it is a significantly less impressive achievement.
I regularly check out how many points I would receive at years end on my games. I've actually tracked this pretty closely the last few games - down to recording score in each category, finish the game and record total game score, then I simply don't post the game. This has let me evaluate the power of various strategies, pointswise. If you take a game like my 900K game, I only received about 30K for the last year of play on it. I don't have the numbers in front of me, but some of the early years were worth 150-200K points per year. I have never played a game out far enough to see the score actually go negative, but it does seem to slowly diminish down to nothing.
So, this has a couple of consequences. First, abundant all, offers the maximum potential for a civilization. Even abundant on anomalies matters as some anomalies offer civilization wide bonuses to the economy, pop growth, etc., along with the cash anomalies offering accelerant for your societal growth. Very fast tech means you reach galaxy wide bonuses sooner and that you have a bigger scoring society sooner, and more points.
Difficulty is a bit more problematic. There is a small multiplier for difficulty. If upping the difficulty slows down your game speed it might actually hurt your score as it might constrain your society in the early years causing you to lose more points than you can gain from the multiplier. For me, I can actually get a bigger society sooner on the higher difficulties because I am getting planets that the AI has more fully developed
and I'm getting the multiplier on top of it.
