IIRC, my first game made it to turn 27. There was a game-ending program error, I had only met one out of seven AIs. Of course, this was only v.0.22
I'm probably going to try PBW sometime here, to find out what it's like to be thoroughly and soundly beaten in SEIV. I'll also have to try 19 TDM AIs on Difficult/High, see if that does anything to me. Only time I came close to being beaten was a PbEM I had going in Beta, back when being the player later in the order of things was a huge disadvantage. I seem to remember scrounging up a 50-ship LC fleet, and having it completely destroyed by a 15-ship BC fleet (Opponent player 1, me player 2). I almost had to change my pants after getting that turn...
To answer the questions:
1. Nope, I didn't bother touching the files in the beginning, just seeing the new interface was enough of a shock.
2. Well, it took a while to get a game to the endgame position, but I was always on top when it got there.
5. TDM didn't exist then
6. Thus far, I've won every game against the AI, usually difficult/high AIs. There's usually a few tight spots in the beginning, but once I get through those, the challenge is keeping the onslaught on a good pace (isolate a system, destroy defenses, capture assets, rebuild defenses, start assult on next system).
Just play around with the AI for a while, and you'll find it easier to beat. You're much more versatile, efficient, and unpredictable than a machine. The AI's major failing is the inability to adapt to an opponent's strategy.