Don't know why there was no entry for comments on that episode. First: Good episode, well done Kyle and Amin. I like the format in which you include poster-comments into your reread.
Second: I found clarification for one of your questions. You wondered how it is with Maester Aemon and his vows (is it possible and stuff).
Your answer can be found here:
http://www.westeros.org/Citadel/SSM/Category/C91/P90/Quote:
Maester Aemon is doubly sworn, to both Citadel and Night's Watch. That is true of the maesters at Eastwatch and the Shadow Tower as well.
So if you are a maester and want to "end" your career in an healthy cold environment, just head on to the wall

Because afterwards you can not change to another household.
As for Aemon's career at the Nightswatch: I think the situation a few years ago was not better than now. Remember: AT the moment Jon could have two maesters: the one from Eastwatch or the one from Shadowtower - both do not fit, nevertheless - they have 2 maesters for 3 castles and Jon prepares for a long wait (Sam has to be trained). So if some maester would step up and say: I take the black they surely would take him.