4500-5500 progress, on 40 planets DIF 5
The average progress to win such a small map is 300-400
However thats an amazing report, and a bug is there too, the Zenith ships should not de-spawn at all. It seems you tried the capture all approach and that is immensely impressing, have you won the game or are you still grinding through the last homeworld? Whats the average raid size? How can you survive cross planet raids?
Well the ai reinforcements are based on progress and how many planets you own multiplied by player count - so yes, the waves will get much more massive without limit, theoretical - i think you are the first to ever play with such high progress ,p
However, DIF 5 means that the ai gets much less reinforcements than Dif 7 - and the ai types you play against are not the most dangerous ones. I don't know what kind of reinforcements you are seeing but on DIF 7 you'd see exclusive core raids and ship composition on all enemy worlds, basically every world would be a core world, and you seem to be lucky not to have a raid engine anywhere.
Well its an amazing report anyhow, i can only speculate on anything beyond 800 progress