RoRo. The first thing to acknowledge in this is that he IS having an affair. It might be emotional and not sexual at the moment, but it absolutely is an affair. You have GOT to nip this in the bud.
Please order and read a book called Not Just Friends by Dr. Shirley Glass (on Amazon and E Bay). I guarantee you will sit there open-mouthed when you read what is actually happening in your life.
A huge and resounding cheer for buying the SIM software. You need absolutely hard evidence when it's at the suspicion stage and when in the grip of something like this, most people will only ever admit to what can be proved.
You will realise from the book that the conditions of your life are the perfect breeding ground for an affair. The child-centred marriage, the complete trust, the husband whose weak spot is the damsel in distress. Your situation ticks all those boxes.
Men very often delude themselves that they haven't crossed the line when they start texting, confiding and keeping secret these relationships. This is because they believe infidelity is about sex. Until that happens, they can carry on without much guilt.
With luck, you have tumbled this before sexual infidelity has taken place. Given the speed at which these things take hold though (texting accelerates affairs because the parties very often write stuff they'd never have the courage to verbalise) I worry that some time has been lost.
What ever the outcome, this needs analysis. If you manage to stop this in its tracks, you haven't solved the real problem. The book I recommend should be read by both of you (once you know what you're dealing with) as it points out how to affair-proof your marriage. The two things I want you to say as your mantra at the moment though are: affairs happen in good marriages. Secondly, the only good friend permissible in a marriage is the friend of the marriage. This woman is no friend of your marriage.
Finally, please update us! Think you might be the first of us to use this software and you could save a lot of people untold agonies if you were able to tell Mnetters that it works.
Good luck and well done. I applaud you.