Question 1: Yes, side fates and quests along with the hunting log( best way to level imo) will help you get to your Black Mage status.......as for starters out side the Steps of Ul'dah will be good for THM.


Question 2 : Yes you can play both jobs they're to different soul stones , you obtain both once reaching level 30
Also the Hym is no longer 10K seals it more so around 500, and for leveling purposes I would use the SCH for easy dungeon ques and use the summoner for doing fates while waiting , you level both at the same time. I would say start allocating your points to MND just for SCH purposes ....as SMN can pump out a bit + Pet at lower levels but if your low on heals while learning how to manage your pet it could be some problems