QWhen playing this card, can I put 4 reserved tokens from my field into my cemetery to reduce its cost by 9?

AYes. The tokens would be put into the cemetery before being removed from the game, so you may include tokens in the 4 cards that you move to the cemetery.

QCan I banish 2 cards from my EX area and put 2 cards from my field into the cemetery to play this follower?

ANo. You must either "put 4 reserved Abysscraft cards from your field into your cemetery" or "banish 4 Abysscraft cards in your EX area."

QIf my field has reached its card limit, can I put 4 reserved cards from my field into the cemetery to play this follower?

AYes, you can.