Since I was one of the ones who asked you, I'm just giving my own impressions. I always imagine the Torah has different levels of interpretation. One of the levels is what we call the world of בחירה, where people make choices and the choices lead to different results. That's the world where most of us see ourselves.
There is another world, the world of ידיעה, Hashem's knowledge. This world is also 100% true at the same time, even though we don't well understand how that works. In that world, our choices and the results are all designed in advance, known to Hashem, built into his world. See the Rambam Hilchos Teshuva 5(5) for his discussion of these two pictures of the world.
It seems to me that a common difficulty people have in reading Midrashim is that Midrashim frequently live in the second world. This one is destined that __ should happen, this event implies __ in the future as a consequence...
But we are used to the world of Bechirah. And the Torah can and should be understood both ways; the people in the stories, their actions, and their attitudes, need to be consistent with their bechirah and free choices.
Anyhow, what you were describing from the Ari z"l is a Yediah type of picture, where there's an overall framework and the characters are filling their parts. It does not mean - to me - that Yaakov Avinu knew his part and understood the events that he was going to fulfill; if he knew them consciously that would actually interfere with his free choices, just as it would interfere with ours.
The Midrashim do frequently hint at people's connection to their destiny, presenting things as if they know about them. "Leah didn't want to have a seventh son because she knew there would be exactly twelve and that meant Rachel would get only one..." but I don't think that should be understood as being in the conscious forefront of their minds, for the reason I gave.
Yaakov may well have been destined to marry both, but the simple reading of the Torah seems to say clearly that he planned to marry only one. And that he was very distressed when he ended up married to Leah instead. His reaction to being fooled - and the Midrash adds that Leah reminded him that this was similar to what he had done to his own father - led directly to his (initial) difficulties in their relationship. All of that is the normal development of events in the world of Bechirah.
Update. I see that I should add: The obvious and correct answer to this question is, Midrash is one thing, and p'shat is another. It is easy to find mefarshim who learn the p'shat differently from the Ari z"l; as I said in the earlier post, I had never seen anything else!
What I was trying to provide here was an understanding of why the Midrash and p'shat can seem to be saying such different things, without that being a problem - unlike the position of so many people I've seen who struggle with them as "contradictions". And, to provide at least one filter that can help a person detect which type of peirush he is looking at.