About a year after we got married, I asked J how he could find it in himself to forgive me.
Yes, I think removing the 'about' will bring more focus into the sentence. Also, next line is:
'He looked at me. "I just did," he said, and went back to his computer screen.'
I's hoping it doesn't act as a damp squib on the first line. The 'sin' is the pivot of the whole story and I'm hoping to bring it to light only gradually. But I also don't want to frustrate my readers, so I would appreciate it if you could tell me how soon you would want to know what it is.
I think this is okay - keeps us wondering, perhaps even a little more. Perhaps change the structure of the sentences to make them more dramatic, although I haven't come up with a good alternative.