Grimm as for resources, ships, delays, speedups, DM, pirates and aliens, it is almost certain that the 89/10/1 rule is valid (based on a highly detailed 75k sample). I can go into details if needed.
Delays and speedups, what do you mean? Speedups are always the same, your fleet simply return ealier (instantly after the expedition)... But yes, delays I've noticed that their return time can vary. I haven't paid much attention to this, but as far as I can tell, the text message seems to have nothing to do with the time it takes to come back. But again, maybe I need to pay more attention.
As for the Aliens, Pirates, DM, Resources and Ships, yes, within their chances, it's a 89% chance of a "normal find", a 10% chance of a "large find" and a 1% chance of a "very large find".
But it's strange, ships have about a 16% chance of being found, but yet, of all the thousands of expeditions I did, I only found a "very large find" 2x when it comes to ships, which they come with this message:
We found an enormous spaceship graveyard. Some of the technicians from the expedition fleet were able to get some of the ships to work again.
The max value of ships found is probably the same as the max Metal value of 105 million metal (x7 eco with top 1 >100 million points). Since in both times I got this message, the total value of ships IN METAL was 76 and 92 million resources. In one I got like 330 Destroyers alonside a crapton of other ships and the other it was like 100s of Battlecruisers, Bombers and Reapers alongside a few thousand probes.
Guess I've just been unlucky with Very Large ship loots.