The problem you face is that whatever adhesive you use will only effect a temporary repair, it WILL delaminate again, how soon or late is a matter of luck, because there is no way you can remove all the old adhesive used in manufacture and new adhesive will not stick (for long) on old cured adhesive.
The only long term options are either a new window if they are available from Miriad Products, or send your old window to EECO and get them to make a new window to match your old one.
Neither option is cheap.
You will have to do something as it makes towing the van with a delaminated window a very dangerous thing, not particularly to you but to anyone following you if the window fails completely and one of the layers comes off the van.