That sounds like a potentially good idea @JazzyJelly.
Have you thought of maybe phoning one of the addiction helplines and getting their take on the situation. Or seeing an addiction counsellor yourself, to help you process your DH's behaviour? That could also help you to make a decision.
Ultimately, though, your DH can work on himself until the cows come home, but he will always be an addict. And whilst he has access to computers, he is likely to relapse and use again. Could you bear to live your life checking his internet history etc, waiting for it to happen again.
After the second time it happened to me, I just couldn't do it again. I knew deep down he would never stop, and he didn't. The stress of waiting for the axe to fall badly affected my own mental health.
Looking back now, not leaving immediately, after I found out the second time, was a mistake for me. It made clear to my ex that I wouldn't leave him over it and there would be no repercussions.
Sex dwindled to once every six months, and then we had gone for a year without at the end. When we did have sex, he couldn't ejaculate without the stimulation of porn. It made me feel rejected, unwanted and terrible about myself.
By that time, I had had our DD and my body bore the scars of that. His refusal to admit to using porn made me feel like it must be me that turned him off. I was so hurt when I found out he was still using it, but in secret, and that was the cause.
It utterly killed my self esteem. That's when I had had enough. It was leave or I knew the stress of the lies would drive me to suicide. It made me so unwell.
I remember how it felt. It isn't me being lovely to want to spare you similar pain. It's just me never wanting anyone else to go through what I went through.
Your proposal seems like a good idea on the surface. But it's one foot in and one foot out of the door. It stops you having to make a decision.
Can I ask you, if a friend proposed what you suggested, knowing her husband was a liar and addict, what would you say to her? Would you tell her that of course he will agree to work on himself, as he tells lies, but would use the time apart to watch more and more porn without needing to hide it, thereby compounding his addiction? Would you encourage her to believe him? Or would you think that any marriage where the issues are so big, that the couple need to split for a while, is pretty much fucked.
I don't think you are fully taking on board that he can and will tell you anything you want to hear. He will lie repeatedly. He is an addict. All that truly matters to him is porn. He may love you as much as he can, but he will love using porn more. He has shown you that.
How much are you willing to take? When any relationship has issues, you have to take love out of it. Loving someone doesn't make them right for you or good for you. Aside from the love, what makes you think staying together is a good idea, given the way he has treated you? I am genuinely baffled.