Well, I incorporated all of these tips and tricks, mainly changing production management on planets and massive colony ship rush, and I WON (on conquest/alliance victory conditions)!
Nice! Thanks everyone!
Now, the good news and the bad news.
The good news is that by the time I got attacked by the second most powerful civilization, I was able to bring up my military research fast enough to fend them off (I lost 4 planets, but got them all back +2 before ending war). So, I was ready for the attack this time.
The BAD news is that once I fended off the attack and switched back to expansion mode, none of the OTHER civilizations appeared to be doing anything! I was at about 2200 strength, the next highest was 750, and the lowest was 37. 37?! It's like they weren't even trying! There were vast swathes of space just empty, ready for me to colonize. It was like 300, 200, 125, 75, 49, 37 for the other civs.
No fun in that!
I fully expected to be confronted by a FULL universe with every faction sharing common borders, but nothing was further from the truth.
Looks like I need to up the difficulty!