Can you order that book onto a kindle app on your iphone to read, or your kindle if you have one and start reading it tonight? It answers all these questions and is so helpful.
I think full transparency is the only way you'll begin to feel comfortable and start to trust him again at the moment.
If he helps you to feel more secure, then trust will grow again. He will need to show you evidence to begin with, this will help you to let go of this pervading sense of: is this just a friend or more, has he been unfaithful, has he been sending her texts that are more intimate? It won't be possible to take his word alone at this stage, as you already feel betrayed and that he wasn't being honest, so you now need evidence. Otherwise every time he stays up late or is on his computer, all you will think is: is he talking to her again?
These concerns of yours will not go away, if he tries to brush it all under the carpet. You won't forget them, unless he resolves to start acting differently.
When I was trying to work through things with my ExH after his affair, I honestly felt like I'd morphed from a relaxed trusting person, into a paranoid maniac. He actually added to my anxiety by not reassuring me. I couldn't let down my guard, until I felt safe from further betrayal. And it will probably be the same for you. Every time he behaves furtively with his phone or similar, any new found security you have will be shaken loose again. Unless he is prepared to be transparent and change his behaviour.
Trust has to be earned again, safety has to be established. This is not an overnight process. You cannot shift from betrayal to unquestioning trust in an instant. He needs to understand that. Also apologies and promises are not enough to rebuild trust; reassurance comes from observable change. He may think that you have a neurotic need to control his every move, which isn't true. Rather knowing what is really going on, is the only way you can begin to re-establish trust. Such as sharing his text messages, e-mail correspondence etc. Only after you maintain a pattern of accountability and safety for a number of months will you begin to relax again I suspect.
My ExH was very ambivalent to this idea and he also had great difficulty cutting off all contact with her. I ultimately discovered the affair had never ended in my case. He was very reluctant to expose secrets and reveal continuing contact, he also only provided piecemeal staggered disclosure of basic information, which really impaired the recovery process. I think he put off sharing everything with me as he thought the truth would only make things worse. Yes the distress caused by sharing would be painful but it would have been a short term reaction but the long term effect is that it would have healed the wounds. Perhaps he was afraid if he truly told me everything, there would have been this atmosphere of nasty accusations and emotional storms, I would have stayed calm. I needed to hear how the affair began, how it ended, what was said, the lies he told etc. So I could make sense of what had happened. But he kept giving me everything piecemeal, which was far harder; every time I thought I'd heard it all, I was retraumatized with additional horror stories. Hearing the whole truth earlier in this process would have helped the recovery and given me more peace. Until I took steps to grapple with shattered assumptions and construct a story about the affair that made sense to me, I was prone to obsessing until healing was complete.
If Your H is wise he will listen to you and be honest. It will help you move forward. If he doesn't, he will only fuel your anxieties and make things worse. He needs to realise that.
I know the above is heavily biased due to my experience from my ExH's infidelity and I know in your case it sounds like an emotional affair at most. But perhaps it will help you a little?