Oscar maybe you will uncover some things in your research that will shed some light on DeWitt's views of Christianity. In many cases the connections that Martin point out are focused on "organization" issues (use of letters, missionary style, social arrangements perhaps....), and I don't think that he goes too far (at least most of the time) on trying to reconcile the inconsistencies. It seems to me that those who try to make Epicurus out to be a stoic go *much* further than DeWitt did in trying to make the Epicurean movement seem like a precursor to the Christian movement.
Maybe in fact that's the way it seems to me that DeWitt draws the strongest analogies -- between them as "movements."
Even in "St Paul and Epicurus" I don't recall that DeWitt said too much overtly in praise of Christianity or Christian ethics, and I don't recall DeWitt EVER stating open disagreement with Epicurus on something, certainly not in the way Cyril Bailey regularly did.
It would be very interesting to know if DeWitt has anywhere ever publicly stated his own belief in Christianity or particular Christian doctrines, was a member of a church, or things like that. Seems unlikely that that level of detail is discoverable today, but if you happen upon anything that would be good to know.