From the main game area you can repeatedly enter the battlefield (BF) to sell excess loot to the merchants there and then exit (inventories get regenerated each time you enter). Merchants can sometimes hang on to some of the things you sell or trade to them, which stay on top of their inventory list. Some people only sell items to the potion dealer in the BF, so they will not clutter up the inventory of the other merchants (whatever value of items they hang on to reduces the available value of the new stuff they can have).
The summoning dolls can hold an unlimited amount of weight, though can not carry quest items, or set/unique equipment in the act it is found. Like your main characters, they can not move once they are over their capacity, but you can un-summon and then re-summon them as needed.
The act 1 doll is the only one who can use a ranged weapon (crossbow), so you generally would not need it to move, anyway. This doll is available on the second level of the game, where you get to after jumping down the pit. If you are past there, you can get back relatively easily once you reach the citadel.
Dolls can trigger area effect traps, but one of the earlier patches removed the ability to use them to open trapped containers. The digital download version has already been updated, as should any remotely recent re-release versions. The version number is shown in the bottom right corner of the main menu; the latest English version is 1.47/1.49 (the 1.49 patch removed the copy protection, but otherwise is the same as the 1.47 version).
Welcome to the forum.
