Possibility of losing custody if an extramarital affair is proven

My question is that my ex-husband and I had a very ugly divorce in 2018 where both parties were involved in extramarital affairs.

I moved back to Canada while he's in Dubai. It's been 2 years that my ex hasn't taken any responsibility for our 3-year-old daughter.

He has threatened me if I take him to court he could get ugly by proving them that I had extramarital affair during our marriage by showing them pictures.

Could that result in me losing the child custody?

Could I still apply for child maintenance?

Would he be accountable for paying it?

Could it be a problem if he shows the court the pictures after 2 years of the divorce and which could result in me losing my daughters custody?

Please let me know. I will be very thankful.