Mooogle quest numbers?

[ElHeggunte]

I believe you only get 3 extra quests when you in fact level up your rep then is goes back to 3 until you level rep again to get another bonus 3.

Yes. Not to pile onto the OP, but the game specifically tells you this whenever you rank up.

I think they cut back the EXP when you were doing any of the tribes that give EXP for anything if you're over the level threshold for that expansion. Like if you're level 50+ you get crap exp from the Ixali, and if you're Level 60+ you get crap exp from the Moogles.

You're both correct. Beast Tribe EXP sees a tremendous drop in rewards once you hit their respective xpac's max level. However, the Ixali already gave very little base EXP compared to the more recent Moogles and Namazu, since this was before SE introduced reward-scaling. That's why instead, as you went through the ranks, they just unlocked new questgivers whose 3-4 offered quests gave progressively better rewards than the last guy and by the time you reached max rank you had something like ~20 quests to choose from every day.