Two different issues here, isitcheating.
one, should you contact your ex
two, should you end your marriage if it is loveless.
Sounds like your ex getting in touch has brought to the surface your feelings about your marriage. He does not sound like a good prospect, and would imo be at best a distration, at worst blow your whole world apart if you start a relationship with him whilst still married.
As mrsboogie said, you need to sort out your marriage first, otherwise this ex could bring it crashing down around you.
sorry to sound negative.
Whatever happens, i dont think you should contact your ex. if your marriage doesnt work out, you will be a single mom with the kids - and your ex doesn;t want any. spells trouble you could well do without. So trust your gut, you said it doesnt sit well with you so, leave well alone and instead, have some time out to really think about your marriage and if you would be happier on your own with the kids.
and no one ever wants to be in a loveless marriage.