Hi there, welcome to FF14

1) Do other stuffs that progress my character or just go beat some bosses that I like the fight. Things that I consider progressing my character such as Beast Tribes quests, lvling other jobs (for story purpose), crafting, gathering, achievements, relic, etc. And if I have a mood, join help some aim to clear party.
2) Every 3-4 months, we got new contents that we can farm. Each to their own if people will get bored or not but mostly not imo.
3) They always try it on every new patch, worked or not.
4) I usually play 2-4hrs. If you only want to keep your character updated to patch, 1-2 hrs should be more than enough imo unless you try to be early group that complete latest savage content.
5) Major patch every 3-4 months, except last patch before new expansion may take 6-7 months.

Bonus : normally it will be Savage raid (Omega : Deltascape savage) but they just added further difficulty called "Ultimate" (Unending Coil of bahamut). Housing, I'm not sure what you want to know about but I can say it's nice place to hang out with friends especially for small FC .

I currently have my friend join the game and he also suffer from 2.0 mainquests too. I understand it but it will get better story will be much more interesting (and yes, less errand boy quests)