-Swamps.You get one suppresed marker for each space in swamp you move?
You get one suppressed token while you are in a swamp, and that token cannot be removed during the supply phase as long as the unit remains in the swamp.
If you receive a second token (say from a MG or Support squad), then that one can be removed during the Supply Phase, but you cannot lose that last one until you are no longer in the swamp.
-Captain Duval recruit tile doesn't have any number on the back. Is it an errata or intended?
I think he might be the equivalent of a Field Command, I am not sure. The Field Commands for US and German forces do not yield VP.
-When preparing the search bag, do you have to place all spells/customizations or just spells/customizations your characters can use (proper coloured bands)?
The rules say to "take all customizations" with the appropriate backs, so you put all of them in the bag.
-Are madness tokens returned to the bag after used or they are discarded?
Much as when a unit is eliminated, once a madness token is discarded I think you put it back in the bag. I don't have any official info on that one at all. I will make enquiries.