Maybe Myitt, but in this incarnation he's getting a little confused. Since it is now physically possible for him to change his mind---see why immortality actually sucks---he's falling for Elayne hard. Myitt's body is sort of irrelevant to him, though in his current state that might change.
And yeah, Oss is pretty much Mar's Morality Pet---someone he's friends with out of a not-usually-acknowledged desire to be friends with someone who isn't Ossanlin at all. Which yes means that Mar getting into this friendship with Oss is pretty damn selfish anyway, but hey give him credit for trying. XP
And actually, if Mar dies
all of it is gone. He'll remember everything, but interpret as one more stupid him among thousands.