Arsh, in your case I don't think you can detach as fast as someone with no kids who has a partner that moves out. You have kids plus your partner is still there with you so there's only so much you can do. You almost have to turn to religion or meditation or something that you can integrate throughout your life because you can't really go many places or be alone long enough to detach. It sounds like you're trying though. You're doing the best you can do in your circumstances. Whenever you and your husband do live separately I bet it'll get easier for you quickly, although there are new challenges to living alone with kids. It would be great if you have family that can stay with you for a while.
For me it's hard to fake anything but I try to keep doing housework when my husband visits to stay occupied. It's so hard to hear his familiar voice, to see his handsome face, and to see him in front of me and yet he's no longer mine.