I think your Husband is using the text messages as an excuse to blame you for what is going on in your marriage.
I cant see where you have cheated on him!!! did you meet and have SEX?? that would be cheating!!
If you haven't slept with this man, there is nothing to throw back in your face, you have made a new friend and is giving you the support your husband should be giving,
Maybe asking for family help to look after the kids, so you and hubby can go out one weekend and talk away from the family home and see if you can sort this out, being in public and talking might stop him flying off the handle and listen..
If that works as family members to look after children once a month so you can make time for your husband.. go out for dinner, stay over night in an hotel, go see a movie.. start dating...
Most of all dont forget to stay YOU...
if you want your marriage to work, 1st step is to forgive yourself and if you didnt sleep with this other man... remind yourself you did nothing WRONG