But even if we suppose he was willing to betray Cyrodiil to save his skin... the imperials are willing to openly betray their own citizens- the Blades, then Hammerfell, and the Talos cult- for their own interests. You've been arguing yourself that the WGC was a necessary evil. So once again, if you're going to blacken Ulfric with such things, what goes for him goes doubly for the imperials.
Well, I would argue that the WGC was a betrayal principally of Hammerfell, but one that can be justified in the light of the presumed suffering of Cyrodiil under Thalmor occupation - the sacking of all cities except for Bruma, the battles, etc, must have taken a heavy toll on civilian life and property, and the Emperor ended that the quckiest way he could. For better or for worse? We shall see.
That said, you have your idea of what's best for Tamriel, and I have mine. I assume we can both agree that the common enemy is the Aldmeri Dominion? (And I beg you not to consider the Empire in League with the Thalmor, for everything points toward a second Great War to come, whether that be with Skyrim as part of the Empire or not).
Who says the Empire is required to unite Tamriel? And what is the Empire anyway? Cyrodiil, Half of Skyrim, High Rock and nominally Morrowind?
The Empire isn't required to unite Tamriel, but given that it has presided over multiple provinces for millenia and that no realistic alternative for Tamrielic-unity besides the Aldmeri man-hating zealots currently exists, I support the Empire against the Thalmor. Oh, and I definitely agree with you in that the Empire has seen better days, but, as I said before, surely the Empire pre-Civil War, encompassing Cyrodiil, Skyrim and High Rock, with resources shared between the three provinces, wouldn't be weaker than those three provinces and Hammerfell individually facing the Thalmor threat alone and divided instead of united under the Imperial banner?