I'm sorry to hear about your difficulties. Some kids require more maintenance than others. I have seen kids who require 100% of one adult's time just to keep them from hurting others, damaging property and interrupting to the extent that none of the lesson gets covered. A teacher cannot faciliate a Sunday school lesson, and other kids can't learn, if all their attention is monopolized by a single child. In most churches, Sunday school teachers are volunteers and there are not many of them. So they do not have the training to effectively handle special needs, or enough adults to individually shadow these children. Either the parents end up having to take their child for most of the service, or the Sunday school teacher gets burnt out and quits. This is unfortunate. My own mother loved teaching Sunday school when I was young, but there was one child in her class who was very violent and she was expected to handle him, but nothing she tried worked. So she quit. It was a shame, because as a result they had to combine classes and all the children suffered. The problem child's mother suffered too, because she was not able to participate in the women's Bible study when she kept getting called out to deal with her child.
I think the best thing you can do is find a church with parents in a similar situation, who can cater to these needs. I know the first church we attended when we moved had very few members with babies. Sometimes we were the only parents there who brought a baby. So when we came, one person was obligated to stay in the nursery with her, even though she was the only one. We didn't want to be that kind of burden, so we tried to keep her in the service with us, but most of the time we'd end up taking turns walking her in the hallway because she would cry. So we decided to move on to another church with other young families. There are three nurseries in our new church, because there are so many babies! It is much more efficient this way, and we are able to spend most Sundays listening the service, instead of tending to a crying baby. And when it is our turn in the nursery, there are always several babies. This makes our church a better fit. I'm glad to hear that you found a church that is a better fit for you.
Not every church can accommodate the needs of all possible demographics. All we really have to go by is "word of mouth." I know my brother is looking for a church that is good for young singles. It is hard for him to relate to people in Sunday school who all have families, or who are all retired, etc. I hope he is able to find a better fit too.