Let me be up front. I respect your optimism and your desire to seek any possible method of redemption before killing Solas. I will likely be addressing a few different viewpoints shared in the thread along with yours, so don't feel as if I'm trying to put you down specifically, if the rest of this post gets to be all over the place.
That being said, I disagree with the interpretation on his hesitation to turn back time and how much his guilt over creating the Veil could be used to influence his opinion on staying in this world vs the ancient one. Solas doesn't lack for compassion and (developing very late in the main story) empathy for other people in current Thedas. His desire to provide some peace for people before he destroys this timeline is admirable, but ultimately doesn't affect his interpretation that this is a terrible future that should never have come to pass, but did because he felt there was no other option at the time. He doesn't hesitate to build personal power or find opportunities to groom the Inquisitor to acquire power themselves if it would benefit his ultimate goal.
Mythal is apparently one of his oldest and most respected friends, and yet he takes her power to suit his own ends because he believes it is one of the fastest ways to gain the power required to make sure he succeeds. He could have easily waited several more decades (or centuries) to acquire power by alternative means, and yet he didn't. After Corypheus was defeated, he could have taken a slower path. He's either in a panicked "putting out fires" mode, or he feels that something coming on the horizon would make it impossible for him to succeed. That may be a double dragon blight. That may be the Veil weakening in places where the pantheon are locked away. It could also just as easily be the risk of becoming too close and involved with people in general, to have too much empathy and see everyone as "real" for him to actually push the Nuke It From Orbit TM button.
Yes, he feels a burden for snuffing out the lives of an entire world so that he may restore the empire and people of HIS time, but ONLY if your Inquisitor is friendly with him. Solas is not quite so caring to an Inquisitor who has built enough disapproval to essentially "prove" to Solas that people in modern Thedas are brutish and unworthy. That close-mindedness, especially regarding his comparison to modern people = Tranquil, is not an alternate path we should ignore when talking about the possibility for redemption. Dread Wolf might have been a moniker given by the pantheon to dehumanize him, but Solas is not afraid to take up that mantle and mindset when he feels it is necessary. Unfortunately, "necessary" for Solas also seems to coincide when he's feeling super emotional in any degree.
That kind of passion, that emotional drive, can be of benefit or detriment depending on how it's implemented. Solas' passions to help slaves be free of their masters and remove their Vallaslin is an example of something beneficial. Killing an agent/friend because they had a slight change in opinion about another faction, but was still in the process of fulfilling the original goal is an example of a detriment. That's panic right there. Panic that Felassen might influence other agents, or worse, defect and start working toward a way to prevent Solas from succeeding. Running to Mythal with his tail between his legs after his orb broke, and then taking her power (it doesn't matter if she knew it was coming) a minute later is also an example of an emotional bad decision.
In our upcoming conflict with Solas, what about Inquisitors who are not quite as invested in saving his soul? There WILL be people who will choose the death-is-redemption option, and there will be others who will only try once or twice to give Solas an alternate path to take. Solas made it pretty clear at the end of Trespasser that while he would welcome the chance for a friend/romanced Inquisitor to prove him wrong, he doesn't believe it will happen. Helping alter his view that all people in modern Thedas are equivalent to Tranquil is on an entirely different scale than "hey, don't do that thing which will restore your home, friends, family, and way of life to how it was before the Veil and allow you to try a different way to prevent the pantheon from being dicks."
By virtue of spending a year being immersed in modern Thedas, and actually being forced to interact with a group of people for 1-2 years, he would have already been on the path to seeing people as "real" without our Inquisitor specifically being there as additional influence.