All armament class types must be 120, everything else can be 115.
You generally just want repairs, engis and scouts in the support slots.
1 or 2 scouts, 2 is good for 1v1s but 1 works fine for general use. (Class your rookie up to recon by the way, doesnt make any difference, just means it cant/wont get classed as a useless fighter/bomber)
Of the remaining slots, you dont want less than 3 of either rep or engi.
My own IJN crew is BO, 2 main gunners, 2 AA gunners, 4 reps, 4 engis and 1 scout.
1.- I don't, sorry.
2.- Torpers must be 120, don't use torpedoes on a BB6. A pair of 120 main gunners must be used on the BB6, if supports are put on the T slots they must be atleast 115, if AA gunners are used they must be 120.
3.- Anything can go in support slots as long as it is atleast 115, or 120 in the case of armament classes. Do not use pilots other than scouts just to be able to use the Amagi. If you have an inefficient or inappropriate crew you'll only do badly/let your team down/get mocked for being bad.