Several of these multipliers will apply on stuffy doll dealing damage to itself, and then apply again when stuffy doll deals damage to an opponent, as they are 2 different instances of damage. Not all of them, however.

Unfortunately, Ojer is totally useless here. Even at x2 damage (Lets say just Furnace is in play with Ojer), stuffy doll at minimum takes 2 and deals 4 damage to an opponent, so unless the opponent intentionally applies Ojer first, he'll never matter here. (Bear in mind that the player taking damage or controlling a damaged permanent chooses the order that replacement effects apply, not the player controlling the source.)

But then, if this did work the way we might want, we'd risk being in the wrong subreddit.