Agree with point 1
Regarding point 2, it seems just natural that, whereas Zigs are quite strong, the minute you put them in your bag, it is your characters strength and not the Zig's which is taken into account, as such it's normal that you can't move when carrying a zig that's carrying 2000 Crystals itself.
As for point 3. Assuming you do a heavy boss with at least 14 other players on a bad day, why wouldn't you be able to carry the 4000/15th share? Even if you're preloaded with 2000 Crystals in your Zig's bag, as long as he stays out of yours you can keep loading more and more...
Regarding point 2, it seems just natural that, whereas Zigs are quite strong, the minute you put them in your bag, it is your characters strength and not the Zig's which is taken into account, as such it's normal that you can't move when carrying a zig that's carrying 2000 Crystals itself.
As for point 3. Assuming you do a heavy boss with at least 14 other players on a bad day, why wouldn't you be able to carry the 4000/15th share? Even if you're preloaded with 2000 Crystals in your Zig's bag, as long as he stays out of yours you can keep loading more and more...