No I’m not saying that at all. It may help you with closure but no you can absolutely move forward while separated. But you have to accept that your marriage is over and most likely you are never getting back together. It’s hard as fuch I’ve been there. I was with my ex half of my live. Like you I have regrets for not putting my best foot forward in the marriage. But I’ve accepted I’m human and made mistakes.
If you want to be left alone then be clear you want to be left alone. Send him a message telling him that you need to grieve and heal. That way you won’t feel guilty not responding.
I’m just afraid your going to be stuck for a really long time because of the hamster wheel spinning out of control in your head that focuses 24 hours a day on how to get him back.