Father has been sporadically involved, now wants 50/50

[Angeldmm]

My children are 4 and almost 3 years old. Their father and I split when I was 5 months pregnant with our first child, got back together after he was born and spit again 3 months after our second child was born. He had a child from a previous relationship, to whom he was very abusive both mentally and somewhat physically .
He had an on and off drinking issue, which eventually led to our permanent split. Once we split, his drinking got worse and he recently went to court regarding custody of his other child (who he had 50/50 wth) but has gotten visitation, increasing to two overnights a month (he works out of town on a two and two schedule). Since he and I split he has been sporadically involved in our two children's lives. In the beginning he wanted nothing to do with them unless I put forth all the effort to make visits happen, dropping them off , picking them up etc. He also told me at the time that if I filed for child support it would be vindictive of me, though I eventually did file for it. He has been drinking on and off since we split, which has caused me to keep the kids from him at times due to not knowing wether they would be safe, and the fact that I had to pick them up on a few occasions because he was intoxicated. He occasionally would ask for more time, and I would grant him that and things would go well for a while until he got upset about something and would harass me , something involving his drinking would happen etc. He also has never wanted to compromise on a visitation schedule , more recently demanding 50/50 (since he has had a new girlfriend for 3 months). I just don't see how the courts would justify giving him 50/50, seeing his other custody situation , work schedule , lack of consistency with past schedules, and taking the kids away from me for 2 weeks at a time. If this were to happen, they would also never see their step-father who has raised them since their father and I split(their step father and father have similar work schedules, so when step dad is in town, they would end up being with their dad the entire time). I am also concerned about the outcome of the situation because before we had our first child, I was accused of DV. It was dismissed, but I had to complete anger management because of it.