B.C.
You came out of a really abusive relationship - and it was absolutely right that you left him.
According to your last post he spit on you, abused you, does drugs, etc.
So now after only a few months you are allowing your girls to visit with him on weekends?
Um - why?
Because he is their dad?
Ok, look - yeah, an ideal Dad is the best situation (and if he was ideal you wouldn't have had to leave him in the first place) but this guy is SO FAR removed from being an ideal dad it's not even funny.
NO Dad is way better than any abusive dad.
Your youngest is not handling this well - and it's not going to get any better for a long time.
You haven't given her the time she needs to adjust.
You have your lawyer talk to his lawyer and have this visitation stopped - like for several years.
I'd want proof he's been through rehab and is off the dope before the kids get any visitation with him at all and it should be supervised visits for a long time.
In the mean time - seriously - get some counseling because you need to heal up emotionally from your abusive relationship - your kids need it too - and it will take years before your ready to be in any sort of relationship again.
For now and the foreseeable future - it should be just you and your kids against the world.
If he's a doper, would he dope the kids?
Is it possible they are going through some withdrawal when they come home to you?