About the theory, in my opinion... Squall not dies in the game. (spoilers) If he die on Disk 1 everything that follows from disc 2 onwards would not make sense, we would not know the role of Edea, the connection with Laguna, Ellone, etc.
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Now, I want to mention the point "Just stay close to me."
There is a translation error in english version: "If I didn't, I wouldn't be talking about it." In the japanese version is: "If I did I couldn't talk about it like this", then she no longer likes Seifer. See: lokasenna.pe.kr/ardente/etc./
One more thing, the line: "I wonder how he felt...?" if I am not mistaken in the Japanese version is: "I wonder what he thought of me", indicating further that among them there was more friendship that anything else.
Speaking as what is presented here, she does not see to Seifer on the dance floor (actually he was not there), but she see at the director Cid Kramer and talk with him. This is indicated in the "Rebellion Princess" page, a page that brought information of Ultimania and other sources.
Also, Rinoa in the game NEVER says and ensures that Seifer was her boyfriend, then obviously they were not boyfriends. It is also important to say that she THOUGHT loved Seifer, NOT assures us even hinting several things: that she was confused with his feelings (for me the most reasonable choice), she was not interested, I had no desire to formalize a relationship with him, etc. And to top Seifer did not know if some feelings / what he thought about her. To me that is not a relationship at all.
For me, they only had a relationship purely business, hence Seifer falls in the summer with the Owls of the Forest, and he has a dream to meet a child (Rinoa is not a sorceress/witch when he met, so it makes sense that he are not interested in her), and apart is a revolutionary type, who loves battles, for he delighted to release Timber, and continue increasing their ego.
If Seifer risked his life by Rinoa can not ensure, do not forget that he never says why, will not know your reason, but remember that Squall is also there, and he is his rival. Seifer fears that Squall and Rinoa are defeated for the Galbadia's army for majority and experience, and that's why going to his aid.
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Squall does not die in disc 4 (spoilers) because the the video where Selphie and Irvine filmed the celebration after beating Ultimecia, everyone is happy, that means that everything went well (include Squall alive).
Also, Kitase in the interview in the Ultimania says that in the game there is a happy ending.