If I'm defending with Ravenbloom Student at the Battlefield Fortified Position, and my opponent comes in with Akali Deadly Weapon, activates the legend ability of Akali and moves Akali Deadly Weapon out, does my Ravenbloom Student survive from the Fortified Position shield proc? Or does Ravenbloom Student die from the 2 damage dealt to it?

No — Ravenbloom Student dies from the 2 damage. Fortified Position's "When you defend here" Shield never procs, because the Student is killed in the Cleanup before Combat is ever staged, so it never becomes the Defender.

Here's the order: Akali moves in → Contested applies → Cleanup runs → her "When I move" trigger resolves, dealing 2 to the Student (2 Might, 2 damage = lethal). In the next Cleanup, the Student is killed in step 3b (Rule 323.5) — which happens before step 7 (Rule 323.9) checks for opposing units to stage Combat. With only Akali remaining, no Combat stages, the Student never gains the Defender designation, and Fortified Position's condition ("When you defend here") is never met.

The Rogue Assassin legend move-out changes nothing: it's an [Action] ability requiring an Open State and a unit already in a showdown, so it can't happen until after the Showdown is staged — which is after the Student is already in the trash. (This matches FAQ #11762 and #11827: Akali's move damage lands before any Shield/defend trigger can apply.)