My opinions
On 3.5: If the game is lagging badly on your turn you shouldn't be obligated to resign unless you're already loosing substantially. You should probably apologise and you definitely shouldn't start a game if you expect to suffer lag like this but, given that games are rated (regardless of how ridiculous the ratings might be) you shouldn't be forced to resign a 50:50 game due to circumstances beyond your control (This is what the wording of your OP implies to me, if that's not the case you might want to change it).
yea, that's what i meant. and as i said within the post, i expected people to disagree using about the same arguments you did. and these are arguments that i can't disproof, because it's a loss-loss situation, and all you can do is decide which loss matters less to you (playing a game with lag/losing a game because of server lags).
The reason I do think that continuing to play is wrong, despite the lags not being your fault, is that it's simply not efficient. If everyone always left games whenever heavy lags occur, personal ratings should stay relatively unchanged on average, beacause the lags should be spread equally. If everyone plays games to their end, the rating is also unaffected, but there will be lot of frustration which simply is not necssary. This is of course a philosophical arguement, not a practical one.
On 6: The thing about saying gg is that people have greatly differing reactions to it. It makes me feel better after a game when my opponent says gg, regardless of the outcome; I assume this is the case for most people as well. Obviously some people are offended by this but I'm almost certain that they are in the minority and furthermore (and I apologise to anyone whom what I'm about to say offends) the people who assume that a winning "gg" is a gloat and get noticeably upset by this are people who I'd rather not play with anyway. So I choose to cater to the feelings of the majority rather than them.
This is definitely the best argumentation I've yet heard for your side. I still disagree though, and I'd make the following point: while it
may be true that most people like it if their opponents write gg, there can't be any disadvantage if you only write gg if the losing player does so first. People like you who want to see a gg from their opponent only have to write gg first, and will still get one. As long as there isn't anyone who, after he lost, needs his opponent to write gg first to feel good (which would make no sense whatsoever) this would be the ideal solutions for all sides.