I'm probably a bad example for your questions, but I'll answer to throw in my two cents.
1. It would depend on the argument. If it was something petty and simple, like what movie to watch, then after she was on me for a while, I'd be laying her down to make her squirm with my tongue! Afterwards, who cares what movie we went to see. However, if it is an 'argument' about a REAL problem, unless it was specifically about her BJ skills, it would be hard for me to even get involved with her actions. Of course, I am a pretty laid back person, very logical, if you get me, there will never really be a need to argue.... maybe remind once in a while.
If our views are that skewed that we can't compromise, then the relationship needs to end, or maybe shouldn't have started. But sex doesn't solve a real problem. (It's like a drug addict escaping their reality with drugs, the problems still exist afterwards, and usually get worse when ignored...)
2. Of my two marraiges, the first was too short to count for this question, and the second, well, when things were good, 3 times a week was actually a slow week. But the relationship fell apart not because the sex slowed down. We grew apart, that happens.... while the healthiness of the intimacy can be a good indicator of the healthiness of the relationship, it is usually not the true reason for things to be falling apart..... AND, MORE importantly, the sexual intimacy cannot be the ONLY thing going for the relationship. I have several lady friends who have spectacular (in their accounts) sex with their partners, but the relationships are beyond the train wreck stage......