Is the contradiction of sincerity in the Two Testimonies - and consequently the non-acceptance of returning to the religion - triggered by uttering them with the intention of forgiveness and the wife remaining under one's marital bond, especially when suffering from obsessive-compulsive whispers concerning creed?

Apostasy does not occur except by certainty, not by intrusive thoughts (waswasah). The cure for intrusive thoughts is to disregard them and consult a doctor. As for combining the intention of worship with the intention of maintaining the marriage, this does not contradict sincerity as long as the intention of worship is dominant. This is not hypocrisy (riya'), even though purifying the intention without any other considerations yields greater reward.