Regarding the helpless Sul'dam, my recollection is that Egwene freed the Damane, and then after that killed the Sul'dam, who realistically at that point weren't a direct threat, and I think it is debatable that a sister who had sworn the three oaths would have been able to kill them.
Perhaps, but I'm not convinced the Three Oaths would have stopped that. Look, we see Joline, Teslyn and Edesina hurl fireballs at an oncoming army of Seanchan. They could have just woven a wall of air to protect themselves from their arrows. But they chose to kill them anyway.
Whether the Three Oaths would have stopped this or not, though, within the combat situation they were in, Egwene did not violate any basic laws of combat by killing the sul'dam. They hadn't voluntarily disarmed, and certainly hadn't offered anything like a surrender, and were quite unlikely to anyway.
True, I think you are right, that there is good evidence that the three oaths have enough greyness within them, that even having sworn them, the same outcome could have occurred. I think it was a somewhat dubious action, but in retrospect not an action other Aes Sedai (or indeed many of the other heroes of the books, including Perrin, though Mat and Rand with their to my mind somewhat warped view of women would be different) wouldn't have undertaken themselves.
Egwene already overdrew before she killed the Sharans. She was perfectly matched with Taim, and had to overdraw to overcome his Balefire. This was a done deal. She was either going to release the source, and be burned out, and completely in no position to stop the Sharans or deal with the new hole in the Pattern, or else overdraw even more and do both those things, risking death. She chose the latter, which is perfectly fair, and was the sensible and right thing to do anyway.
Fair enough, given those were the options, then yes I think either option was valid, and the option chosen the best thing for everyone involved, and the more selfless, especially as there is now potential that being burned out can be cured. I think I can see why Cannoli has a differing view on this one, but can't agree with him myself on this one.