Stop sanding the paint! I'm sure you already figured that out. Sanding isn't necessary in this situation. You did everything right and the Kilz primer sealed the walls. The problem is the Glidden paint, possibly a bad batch. It should have cured after 4 weeks.
I recommend you reprime your walls, sealing the Glidden paint. Kilz Oil Base is a very good primer for this. Allow it to dry overnight then paint with the Ralph Lauren.
The Ralph Lauren textured paint is difficult to use. Make sure you carefully read the instructions on the can. It will hide some imperfections, but don't be surprised if some still show. Plus it doesn't cover as well as paint. Plan on at least 2 coats, maybe more.