Three months, even if he is in recovery is a very short time. My ex was in recovery with a sponsor, working his steps, but after only 90 days was still a hot mess!
If you are not sure, you should not decide anything, more will be revealed. I know it was hard to make the break, don't be too quick to undo it.
I would definitely consult an attorney, just to know where I stand. You don't have to do anything, but I bet you will feel stronger just knowing.
Take care of you and those precious children. You sound like a great mom