I wasn`t able to follow the whole discussion, but here are some random thougts:
From one of the last Adventures I (as a Male, btw.) mastered, I saw that male players seem to have problems to avoid sexual jokes. In the adventure I speak of, the group`s Bard and a female NPCs came together - Wether I as the DM nor the Bard`s player did describe anything directly sexual ... contacts, and every of the other players seemed to be forced to make jokes about it (more or less In Character) - they believed the two would never do "it".

During gameplay, I didn`t notice this much, but it annoyed the Bard`s player.
Well, to make it not too long - and it is just an example: You see my assumption above.
If you encounter Off Topic discussion during the game, it might also be, that some of the players became bored.
This can happen easily when they are not primary involved, like a "social-type" character during a combat-heavy session, or a fighter-type character during a social-heavy session.
The best way to counter this, is to have both parts.
Try to make the Fighting a reward for the social-type character (like finding some important clues, capturing someone with information about the story), or the Socializing a reward for the Fighters (like finding the way to a dangerous Dungeon full of Monsters, finally getting the criminal for the final battle).
And try to give out information in both cases that are important for both sides. (During a fight, some of the combattans might utter some important names, or an NPC gives valuable information about fighting style of a possible enemy..)
Oh, and you can start being a Master anytime - preferably after you learned the basic rules. But I think after 1 year of play, you should be ready for it - everything you can learn than for being a master you learn by being one.
It is alway good to ask the players if they liked your adventure, what should have been improved, what missed and so on...
Anyway, mastering is never easy, and you have to accept, that guys are guys, girls are girls, and that Off-Topic discussion is something very usual.