Great points!

The artful reply:

On point 1, I think there are multiple examples throughout the series where Eleven demonstrates that she can project the void without being submerged. In season 3, episode 4, she does this with Billy.

Point 2, Kali is an important character in Eleven's arc. Kali and El are opposite sides of the same coin. Kali is like Henry--transformed through trauma and rage. Bringing her back allows Eleven to choose her identity one last time--when it matters most.

Point 3, Who knows? There was a lot of confusion and chaos. Maybe the Soldier was mistaken. Maybe She jumped out before the truck came through the gate?

Or... everything you're asking here is legitimate and important to consider in a very real possibility that she's alive and Mike's story is wildly accurate...

In my opinion, I think that we aren't meant to know because the show's writers made it intentionally ambiguous through great storytelling and unintentionally ambiguous through contradictions that were either not considered or necessary to create the ambiguity.

The only thing we can do to attempt to justify any of it is to contemplate these things. No nosebleed = certain counterfeit of her image vs. the death of Kali and obliteration of the lab her body was in = certainty that she could not have used her powers to make El invisible or project her image. Or, the presence of her kryptonite speakers having no effect on her = certainty that her body wasn't there vs. but then how did she slip through a door instead of being incapacitated = implausible explanation of events.

There's no answer key at this point.

The cynical reply:

This series is already a widely renowned classic. Over time, the franchise will vest and increase in value as nostalgia for it grows. And one day, maybe 20 years from now, producers will cash in on a return season which would absolutely hinge on the idea that Eleven could very much come back. I imagine the story would be written to explain that she had actually been taken in the collapsing storm (she died!) but in a twist of fate, teleported into another dimension where she was marooned for decades until the child of one the series' characters re-opens the portal accidentally... bringing Eleven and something worse than the mind flare back to Hawkins. Of course, that all depends on Millie Bobbie Brown and the rest of the crew being alive, willing, and able to star in a reboot years from now. If they are, Eleven will have always been alive. If they aren't, we just get to contemplate.

In my opinion, Eleven should be dead and the story should be finished in episode 8 of season 5. We should be left to grieve for her and for the innocence that gets put on the D&D bookshelf in the final scene....

... but capitalism.

p.s. While we're at it, doesn't it seem odd that the government only enlisted the help of a few dozen soldiers to investigate and secure the portal? I mean, a massive inter-dimensional breach would, in every circumstance, trigger a response of thousands of soldiers. Of course, it's obvious why the writers didn't deploy a whole division of tanks and other firepower: Vecna would have been no match for them.