Does my fiancé have a chance at getting 50/50 custody of his kids?

So me and my fiancé have been together for a little over 5 years. I have 2 kids from a previous relationship and he has 2 as well from a previous relationship. When me and him first got together, he was able to pick his kids up everyday until evening and then would take them home. Winter came, the mother stated she didn’t want them out in the cold so much so he could only get them every other weekend and that he didn’t have a choice. After this happened, court papers came in for them to establish child support and custody. She was granted physical custody and visitation is based off of mutual agreement. Well she only allows him to get them every other weekend. Every time he ask for extra time, she states they have plans. He hasn’t been able to get them on any holidays either. She is always switching up weekends to suit her needs as well. For example, tomorrow he is supposed to pick them up for the weekend. But it is his daughters birthday so they have “plans”. He has to wait until Saturday to pick them up. She just texted tonight to let us know they have to be back Sunday morning since they have more “plans” again. She is always screwing him over with his time. He is a great father and gets so upset because it is out of his control. Child support takes pretty much half of his check every week so we cannot afford a lawyer. Would he have a chance at fighting in court without a lawyer? He wants one week on, one week off. He knows she won’t allow it simply because the child support would get lowered. His kids always ask why they can’t come over more and always say they want to live with us. They are only 7 and 5 so I know they can’t speak for themselves in court. We are fully capable of being able to care for them half time. I do not understand why she doesn’t see that’s what would be in the best interest for the children. Do you think he would have a fighting chance without a lawyer? We are in the state of va. Oh, me and him have one child together and have another one on the way. So they are also missing out on being around their siblings more often.