And though channeling seems to be restricted in the presence of the Dark One, this may only be limited to the followers of the Dark. Else, how would LTT and the Hundred have managed the Strike on SG in the first place? They used the power for both their attack and to place the seals. So therefore, channeling is not impossible near the bore.

The limitations on Channeling might only be in place in/near the bore where the Dark One has the most control.

Besides this, Callandor can still be put to great use in other places and times during the final battle. Rand still has a lot of Forsaken/Dreadlords and shadowspawn to kill.

As for the rest, about trying to force modern marital morals onto the story, it has no place. Especially when you consider the sexual morals of the rest of the world at large, the Aiel specifically.