If you're really hoping that the next 8 weeks will turn him around, then acknowledge that. Are you doing it for him - for the SD?
Maybe, if you walk away now, he'll be forced to spend time with his daughter and bond with her - it could be the best thing that has happened to them.
Your relationship with him sounds tenuous at best. Do you have any plans to marry - any commitment in the future? Or will he continue to pretend that he is single and sometimes has his child for visitation.
Good luck - I've seen this dance before.
Perhaps you can still be a figure in her life. Don't give up on her just because you and her Dad didn't make it.
Speaking from experience....the feelings of abandonment and rejection have a lasting effect. Please talk with her and work something out for the two of you.
DS (6), DS (18 months)
Aug 30 2013 He gives me back his ring with an ultimatum: "Get over it or get out".
Status: Done like dinner