As for your daughter's husband, even though you mentioned he "said" he was a Christian, I think this verse still applies:
1 Corinthians 7:14-15
King James Version (KJV)
14For the unbelieving husband is sanctified by the wife, and the unbelieving wife is sanctified by the husband: else were your children unclean; but now are they holy.
15But if the unbelieving depart, let him depart. A brother or a sister is not under bondage in such cases: but God hath called us to peace.
My first thought regarding his sudden actions were the same as Heather's (Acts'): Possible bipolar or other mental illness. Been there, done that with my own hubby. I didn't notice anything unusual about him until he had his breakdown not long after our second child was born. Many times bipolar will manifest in response to a major life change, like a birth, a death, a marriage, a divorce, a job change, etc. I say let him go, if he is so intent on going.
As for the "church" you are/were attending, I am appalled at the behavior of the pastor and the deacons/elders. That is absolutely NO way to shepherd a flock!! I agree that you should seek another, more Biblical-based, more accepting church family. If you lived near us, you would absolutely be welcome in our Baptist church!! Church should be where hurting, flawed people go for Biblical help and support, not castigation and shunning. We all have our flaws, our faults, our issues, and being a member of a church does not shield us from that. Our pastor readily admits his own faults and failings, even from the pulpit in the course of his sermons. He knows that being a pastor does not make him "holier than thou" or immune from the same problems as his congregation. We reach out to those who are hurting and dealing with issues: that includes a ministry to a men's halfway house just down the hill and one in the next county. Our local tourist town once had a resort area minister who suffered from bipolar disorder and who eventually took his own life -- some of our men were involved in the search for him and our church ministered to his wife and young daughter. THAT is what part of the mission of the church really is -- to meet people's immediate needs and, through that, to lead them to Christ. There is NO WAY that any of you have lost or will lose your salvation over this. The Bible says that NOTHING can separate us from the love of Christ, and "nothing" means "NOTHING"!!
So my suggestion is to start looking for another church. Start attending other churches in your area, tell your story if you feel comfortable, and see what their reaction is. While I'm not suggesting you find an "I'm okay, you're okay, feel-good Gospel" church, you and your family need the love and support of a body of believers that believes the uncompromising Truth of the Bible.
"Oir is leatsa an rioghachd, agus an cumhachd, agus a gloir, gu siorraidh, Amen." ("For Thine is the kingdom, and the power, and the glory, forever, Amen" -- Scots Gaelic)