I think you mis-read it. Please re-read it again and again and again.

I can only ask for your support to have the time to “show, not tell”; and in the meantime express my sorrow at having caused pain.

I will rewrite this for him.

"I can only ask for your support to have the time to "show, not tell"; and in the meantime I want to show you my sadness, regret for causing you feeling distress and uncomfortable."

I replace express and sorrow with definition coming straight out of a dictionary.