My ex has been recently threaten to take me to court to gain 50/50 custody of our kids. I have on several occasions offered every other weekend visitation but he is damanding 50/50. He has been a known drug user for the last almost 10 years has been in and out of jail several times. Recently moved in with a girl after dating for less then a month. Has no license or transportation lives in a two bedroom apartment with no beds for my kids. What are his chances of getting 50/50

Where?

Go to Court and PROVE your allegations, PROVE he's unfit. Is 50/50 even practical with at your children's ages?

I find that people who threaten are good at one thing - threatening.

... Recently moved in with a girl after dating for less then a month. ...

So? Were you ever married to him? If not, you had extramarital sex with him as well. I fail to see what the length of the pre-cohabitation dating period has to do with the price of potatoes in Potsdam. Please explain.

Well, apparently the children are over 10 because he's been a known drug user and in and out of jail for about 10 years... and no way would OP have sex with a known drug user who is in and out of jail.

Good catch on the living arrangement.