Manual shipping & two distribution points

Hi,

That won't work. What you could do though is to use volumes for that differentiation.
For example, all the products from distributor A would have a volume of 1. The ones from distributor B would have a volume of 1000.

Then, you would have two types of manual shipping methods. The ones with a volume < 999.5 and the ones with a volume between 999.5 and 1000.5, between 1999.5 and 2000.5, etc.

That way, if the user tries to order products from both distributors it won't let him (if that's what you want, otherwise, you can have a third class of shipping methods between 1000.5 and 1999.5, and between 2000.5 and 2999.5 , etc).

No, there is no option for that.
That would require to create a new shipping plugin for HikaShop.