Is helping one's husband masturbate via text message permissible or forbidden, and what is the correct course of action in this situation?

If the marriage contract has been performed, there is no harm in discussing matters of pleasure and intimacy with the husband. However, this should be avoided via communication channels due to the possibility of them being breached. There is no sin on the husband if what he incites is merely talk. As for masturbation by hand or similar means, it is forbidden.