You are torn and so you have justification for ea. point of view thinking alanon is for staying and therapist is for going. With the two sides being equal you don't have to make a decision. No alanon literature advises us to stay in a relationship with an addict. It does advise us to be in recovery ourselves and become the very best we can without being sucked into the undertow of the addiction. Only you can decide what to do about your relationship. Me personally I would not tolerate infidelity or addiction.