Welcome back, I am sorry to hear that he is back to his old tricks of texting this girl. I had hoped that he would realize how this is effecting the relationship and stop.
It sounds like things are getting real bad real quick. It may be time to take a step back and take another look at what you want. It is unfair for him to continue with this after you have asked him to stop. Innocent or not isn't the point........when you are in a marriage you have to make certain sacrifices and one of those is to not do anything that can cause pain to your spouse. Continuing conversations with a women who has professed feelings for him is not only wrong of him but unfair to you.
I would suggest taking a step back and do some serious thinking. Between all of his actions in the past and this behavior it sounds like he is not taking this marriage very seriously. You have a couple of options here.
The first is to stick it out and keep trying........in other words accept his actions and hope he stops soon. I can tell you that as long as you allow him to control you and allow him to continue to do what he likes he has no reason to change. Marriage counseling is great, but if he is not willing to make the change then no amount of counseling can make him change.
Your other option is to take a firm hand with him, let him know that this has gone on long enough and you are done with it. You have a couple of different routes you can take with this option. The first is to take a small break or separation. You can request that he leave the home, or you can leave for a short time to try and show him that you are serious. Or you can put new rules on the relationship such as sleeping in different bedrooms and living more as room mates for a while.
Either way its time to sit down and talk with him. Let him know that his actions have continued even after he promised to stop. If he gives you the excuse that it is innocent explain to him that is not the point. Innocence has very little to do with what he is doing. Anytime a man goes forth with a emotional bond with a women other then his wife it is wrong. You must be firm with him and let him know that you have no intentions on continuing to be made a fool of. Let him know you have already given him a chance to stop his actions and yet he continues. Let him know that you feel like he has betrayed you over and over and yet has no plans to stop.
At that time you need to let him know what you plan on doing about it. Do not make idle threats. Make up your mind about what you want to do and then be firm. I wish I could tell you that this will be enough to wake him up and show him you are serious. But the fact is I can not read the future........The fact is things can not remain the same something has to change. Hopefully he will see that you are serious and really begin to work on the marriage instead of faking it.
The reality is no matter how much you love him, or how much he loves you. He feels like he is in control and can do what ever he wants to do with you. Every time you allow him to do it he gains even more power. By standing up and making your own choices and being firm with him you take back your control and show him you are serious.