I think he probably would avoided the suspension, had he not continually did things like that. He exhibited a pattern of behavior that leads credence to the earlier complaint. The old saying where there is smoke there is fire.
Agreed. I don't think there would have been an investigation at all if the incident with the girlfriend had been an isolated one.
It's probably "unfair", but I get why the NFL did it. Like @ross1998 said, the accumulation of all the little dumb stuff was going to get out of control eventually. Better to correct the behavior now.