At this point in time you really have nothing to lose in trying some of that ' windshield silicone' sealer.... a couple of dollars... but the trick is to carefully clean under the rubber around the windshield... which will take at least an hour to do a good job... but could sure be worth it.....use an old t-shirt material pulled tight on a narrow spacking scraper.... and something like Klix88 grease and silicone remover.... available in gallon cans to wipe cars after all the primer and sanding has been done to remove hand print oils before shooting paint.
Remember to do the inside rim also..... and follow any other instructions on the tube.... with regards to temps or cleaning methods....