Wa `alaykum As-Salamu wa Rahmatullahi wa Barakatuh

You only have strong doubts on your ex-husband but those doubts have not come to be certain. There is no problem to raise those doubts and problems before a judge, if they are beneficial and necessary in the case.

This is one of the reasons a person may backbite others, i.e. if he/she files a case in court and should provide reasons for divorce, etc. You do not have the right to talk badly about him in front of other people.

You must repent to Allah of this sin and if you are able, try your best to ask for his forgiveness and try to facilitate his seeing his children regularly.

 

Almighty Allah knows best.