1: Yes, you can get a personal chocobo through Grand Company quests.

2: Arc can use some of the cross class abilities well, there are many to get your hands on like invigorate, sentinel and so on. At lv 30 you can gain access to the Bard job, if you so choose, and it is useful in party play. You lose access to abilities that are not from CNJ/THM in exchange for access to BRD abilities. If you intend to be BRD, I'd suggest working on those two.

3: Craft for fun, or if you're bored. Just pick one you like, as you can level them all on leves with patience, or find ingredients and grind your xp for whichever craft higher. The DoLand (BTN/MIN/FSH) are 'easy' to me, I find them relaxing. They're a great way to make money, much better than crafting is at the moment.

4: If you're soloing, depending on mob type and level, your attack and defense ratings can start to get pretty important. If a mob is too high above you, due to formulas in the game, defense won't do a whole lot. I always tried to upgrade at the new sets. 18-20, then 25 + 35 + 45 and just fill in the random gear where needed. As long as you're killing mobs or doing leves you'll be making plenty of gil. In XI farmin for gil was a nightmare, in XIV its really easy. I've never had to "go farming" to buy the basic gear I needed.

5: Leves are great yes, you can generally find mobs, approximately, of the level of X camp near X camp. Example: Drybone - around Drybone you should be able to find mobs that are generally 10-20. Feel free to explore some. Low level parties can be hard to come by. If you see one forming ask to join, or attempt to start one by shouting yourself... I might just solo because I hate to sit idly in town.

As it stands now, no. We can't decorate rooms yet.