It would help me to understand your assertion that this episode was not one of Smith manipulating Kimball if you could explain which Gospel ordinances offer salvation to third parties.
Kimball was told that, through her actions, the exaltation of her immediate and extended family could be 'ensured'. Yet, according to my understanding of Christianity, the only proxy through which one person's sins can be absolved is the Messiah himself.
Again, what ordinances are available to me wherein the actions I take can guarantee the exaltation of any other person?
In the Old Testament, priests had the power to "atone", through the Law of Moses:
32 And the priest, whom he shall anoint, and whom he shall consecrate to minister in the priest’s office in his father’s stead, shall make the atonement, and shall put on the linen clothes, even the holy garments:
33 And he shall make an atonement for the holy sanctuary, and he shall make an atonement for the tabernacle of the congregation, and for the altar, and he shall make an atonement for the priests, and for all the people of the congregation.
34 And this shall be an everlasting statute unto you, to make an atonement for the children of Israel for all their sins once a year. And he did as the Lord commanded Moses. (Lev.16)
After the death and resurrection of the Messiah, he could likewise appoint his prophets to make judgements on his behalf. His word, whether it be by His own mouth, or the mouth of His servants the Prophets, would be the same.
That would depend on whether one held Joseph Smith in the same esteem and authority as the ancient Prophets.
It appears that Helen Mar so held him.