I have seen three different post by PLAYERS who say that an imbalance of MS is Milking/Pulling. It does not, however, say that explicity anywhere in the rules. So would it be possible to get a definitive declaration about this preferably from Zorg himself or at least from a Mod?

Conversely, they can rec the DF around their planet as long as they send it back to you. Or you both sent the same ships the same amount of times.

Being realistic, it is not sending resources, so I would say go ahead. Really, what is anyone going to do? Zookon fed his entire fleet away once, Rukai did the same. If they were going to get someone in trouble for having ships die on somone's doorstep intentionally then those times would have been the case and not a few little moonshots.