I think I would have to say that churches that begin from a split start out crippled, and may never completely recover. I wonder if the folks who left the church really went about confrontation and correction in a biblical way – i.e. following Matthew 18:15-20, etc. Were those who said and did wrong things confronted with their error, or did folks just get mad and leave? Far better to confront the sin and the division, and come to true unity.
If this were a marriage, would the offended part simply seek a divorce? I think not.
I guess this is my way of saying that I have my doubts about both those who remained, and those who left. I suspect you have some of the same doubts – and you know much more than I.
I would seek to confront the split off group with the biblical issues, and see how they respond. If they will not respond biblically, I would not involve myself further with them. If they do seek reconciliation, then so much the better. I’d help them all I could.
There is the possibility that the split off group will take your counsel, and yet the outcome might not be good. Then the division will be biblical, and the chances of success in a new church are better.
The Book of James is a good one, as is 1 and 2 Corinthians. In 1 Corinthians Paul starts right out with their divisions, and shows them to be rooted in the flesh. By the way, Philippians is a great book on this as well – focusing on joy, humility, and servanthood. (Actually, I have a series on each of these books on the BSF Website. Above are the links)