My husband had an affair which ended 11 months ago. I was suspecting?

something and took his car keys. He then walked to meet her and then got drunk for some reason. Looks like she then left and he sent her a text saying "You are mine, come back". When he came home I checked his phone and saw the texts they were sending each other that night. When I confronted him, the affair ended. But the first thing he did was send her a text asking "Are you ok"? He however wrote her a letter after the affair ended saying things like "I selected to leave my wife for you", "It feels like a bereavement losing you", "I will love you until the day I die", how he regretted the fact that I found the text etc. He however later on sent another e-mail to her saying how he didn't mean anything and that it was an ego boost, how he lost his best friend etc. I did not know about the first letter but the mistress showed it to me after I didn't leave her alone. It was the following day that he send her the mail. I don't know if he only sent it for my eyes to see as it was sent from our home computer. And does staying with me mean that he loves me more than her - or could it be only because of our 2 small daughters, ages 4 and 8 and because we have been married for 20 years. Also know that he also had an affair 15 years ago and this current woman was one of his best friends' wife. If he does still care for her, why is he not with her?