Sorry to hear about the grandmother. Any kind of emotional pain or loss can really affect the emotional/mental balance when starting to deal with CSA issues. you usually either become hyper-sensitive to everything and totally lose it or just shut down completely. Hoping for him to regain whatever looks like balance for him soon. He no doubt has developed his own coping tactics that have helped him get this far...
You are right on about not pushing - but gentle loving nudges are sometimes helpful - especially if you put it in a "WE/US" context to reassure him he's not alone in this.
Meanwhile, we're all here (both survivors & supporters) for both of you, if and when you need to vent, question or share the ups and downs...
"My experience has shown me that I all too often tend to deny that which lies behind, but as I still believe, that which is denied cannot be healed." Brennan Manning, "All is Grace - A Ragamuffin Memoir"