The way to stop Benny and Chikadee from syncing up is to look at them on their respective hallway cameras because that slows them down. For example look a Chikadee more than Benny if both of them arrive to the hallways at the same time so you slow her down, then Benny gets to your door first then you deal with him and then deal with Chikadee. Or you can do the opposite. It is also explained in the dev logs you see when playing the nights. Make sure you read them.
As for the other thing make sure you keep the light on Benny all the way until he leaves. Maybe you turned the light off before he actually left. Don't turn off the light yourself it should turn off on its own if you scared Benny away successfully.
Anyways I wish you well, God bless.