Terrific evidence, but not outright proof. But as Loghain usually dies based on other crimes, it is irrelevant.
Evidence for what? A tactical retreat? The king probably faced the bulk of the Darkspawn horde, which you as the Hero of Ferelden only dared to attack with the combined forces of your contractual partners and the troops of the Ferelden high nobility. How should Loghain sucessfully attack them alone?
I think it's maybe the point where you should drop this certain part of the discussion. More or less repeating the statement you began with is not the goal of a discussion and it certainly won't make your opinion more true or logical. I've seen this attitude from you in several threads. If you can't come up with logical and valid arguments, it's pointless trying to convince others of your opinion. Everyone can have his own view point, but this kind of argumentation is really unnerving.
Meh, there is no right or wrong on Ostagar opinions. There's only bioware's inability to commit to either side because they relish on the drama. There is only just strong opinions at the end of the day. Talking to Threnn, Solas and Varric about it pisses me off to no end. Glad I did not use that as a base of why I always execute him because for me Ostagar has always been a grey area.
I'm curious, what did they say? I played Inquisition and probably asked them, but it slipped my mind. 
I generally disagree with executing Loghain, as I stated in my first post here in this thread. I think the only despicable thing Loghain allowed himself was the selling of elven slaves to these Tevinter bastards. Concerning Arl Howe, it's unclear whether Loghain knew about everything he was up to. Howe is a snake and as member of high nobility, he would be able to intrigue and persue his sick plans without too much resistance anyway. Certain points Loghain states are really valid, if you're thinking about it. He stood up against the Orleasians, fought countless times for his homeland and king while others sat idle and did nothing. He deserves a chance to die a hero's death, if not even to live on (although that's hardly possible without the dark ritual).