As long as Assad will not spare the civilians he will be definitely on the loosing side because every shell or bomb dropped on civilians will recruit more people for the FSA and the radical groups in Syria.
Will the FSA be able to unite all of those groups and fight like a regular Army? I don´t think that will happen before this war ends. Are there acts of terror happening in Syria? Well for us obviously on both sides but i think the people in Syria don´t see their actions as terrorism but more as an eye for an eye. So i think before the opposition can unite and enforce any rules of warfare they would need the see the things with our eyes but then again what are you going to say to a father who is digging out his family from the rubbles of his house.