Any anomalies in asteroid density and drop rate is randomisation on Freelancers part, FLHook not working properly or simply personal perception fooling you.
Every field has its loot probability and amount set to the exact same, similarly with the amount of dynamic asteroids flying around.
And the fields should regenerate at 100000 units per minute if the lines are working properly.
Some mining fields within an asteroid field are defined within a seperate ini, hence why some dynamic asteroids in the field have no loot. But the mining field itself produces their 20 dynamic asteroids around you independent of that.
Regarding PScrap@Valence: I've updated the OP while the server file changes only apply at the restart. Valence should have the price then.
And yes, Freeport 11 should have its Core bribe restored soon. I also like the idea of making Valetta and Tripoli other full-efficiency salepoints for PScrap, but hesitated to put it in for now to give it some more thought.
In raw format, every asteroid field has these settings for the aforementioned behavior.
[DynamicAsteroids]
asteroid = <dAsteroid_arch>
count = 20
[...]