Ok, I will do my best here...
He will be able to live with you in Charleston, likely within hours of his arrival. He will just need to let them know when he shows up that he has his family in Chas waiting on him. If you wait until he gets there, you should be able to move into base housing, saving you a bundle in deposits. Base housing in Chas is not bad.
I think anywhere from 60-70% of students stay in Charleston for prototype. I am not sure having a family has much to do with it. They will ask for NY volunteers, but in the end, you guys will go where they say to go

(Get used to this mantra "Home is where the Navy sends me").
He can volunteer for subs, but only a SMALL percentage of submarine sailors are on trident submarines, which has the schedule to which you refer. There is *NO* guarantee that he will be assigned to a trident submarine. Fast attack sub schedules are much more unpredictable. To assume that he will have that convenient 3 in/3 out schedule is setting yourself up for heartbreak later.
Once you get to a real seagoing command, there will be spousal support groups. My wife, however, has done well just getting involved in school, work, and play groups for the kids. She meets other spouses and through that dynamic, forms her own little unofficial support groups.
Will it be hard? There will likely be hard times, but then again, who doesn't have to get through difficult times, military or otherwise?
Good luck.
