1. He didn't take memories from Buffy's mind. He begged for her life. The Oracles handed him the time fold. They made the terms; not Angel. If you have beef with that, at least direct it in the right direction.
2. If we are talking about memories being messed with than the fact of the matter is that the only person whose memories were actually altered were Angel's. That version of that day exists in his mind only.
3. Those memories that he "stole" from his son were the same memories that led said son to try and blow up himself and a shop full of people. When those memories were returned to his friends, was there a single one who was happy for them? Better for them? I see very little difference in what the Monks did with Dawn and what Angel did with Connor. He gave up his son even knowing him so he could have a good life. And yeah, it didn't work out and the lesson that you cannot mess with those things was clear. But so too was his motivation: love. It wasn't the same as Willow masking Tara's memories for her own gain.
If it was my child and I had the option of taking away the kind of pain that Connor was feeling, I wouldn't even hesitate.
4. Was it a suicidal mission? Absolutely. But if you are trying to bring down one of the most powerful forces of evil on Earth, well...the mission tends to be of that nature. He had no idea that L.A. would go to Hell because of it. No more than Buffy et al had any idea what devastating effects creating all the slayers would have. They were acts of sincerity and conviction. Never was Angel's intention to hurt people. In fact, his entire MO has been to avoid that as much as possible.
He was told, by arguably his most trusted source, that if he didn't become Twilight the entire world would go to Hell.
I have yet to see any evidence that that was not true.
No, it was Angel. Right up until Kitty!Twilight took over his body, it was all Angel. Was he operating under questionable advice? Absolutely. But like I said, he is loathed now for his choices, but that doesn't mean they were not the right choices to make.
In order:
1) Granted, Angel was manipulated by the Powers into believing that he could somehow alter Buffy's fate (that she would die protecting a loved one) by renouncing his humanity. Over the course of the series, Angel has been manipulated be the Powers That Be, The Senior Partners, and Twilight into doing some very extreme and somewhat questionable things, most of of which involved his takinng freedom of choice away from others.
2) You have this one backwards. The only one who's memories weren't altered by "taking back the day" were Angel's. Everyone else lost theirs.
3) "Stealing" Connor's memories, regardless of whatever nobel excuses that Angel might have come up with, is exactly the same thing, for arguably the same purpose, and on a far greater scale, as Willow stealing Tara's memories, and we know where that led. We would all like to make the bad memories go away, and having the power to do so would be awesome, and a terrible temptation to use in order to protect our loved ones, but it is as much, or maybe even more, from the memory of those bad memories that we learn and grow.
And, finally
4) By his own admission, Angel knew that attacking, even destroying, the Circle of the Black Thorn, would in no way change the Senior Partners' plans, and would, at best, only delay them slightly. Destroying the Circle was Angel's way of spitting in Wolfram & Hart's collective eye, a gesture, most likely as futile as a gnat attacking a grizzly bear. If the end result had only effected himself and the members of his crew who were given the choice as to whether or not to share that risk with him, fine. However, Angel's gesture resulted in placing every man, woman, and child on the Los Angeles area at risk andm in fact, sending them to hell. And the fact that he managed, later, to correct his mistake (using, ironically, the same method used in "I Will Remember You," though without the instant memory wipe this time)
Angel's "most trusted source," who he has known for only a matter of minutes, tells him that the only way to save the world is to destroy the entire universe, leaving Buffy and himself the soul survivors, and, hopefully, the new Adam and Eve of the Twilight Universe. THAT most trusted source. Right,
And, as for whether or not Angel's choices were the right ones to make, I fail to see how total genocide could be considered right or even expedient by any interpretation.