As much as I apologize for your unenjoyable situation, the hardest thing to realize with many products is that when they aren't working as expected, there is a certain point in time or degree of defectiveness to which a return can be made. Now, I'm not sure why your salesperson had you wait longer past the initial month... they really should have suggested you bring it back within the 30-day trade-in time period.
The inch to inch-and-a-half difference is one of those things in the gray area. Although we would very much like to have you be 100% happy with your purchase, if a product is not returned as defective in the allotted time, they have to follow the set out measures as to what items may be returned. Unfortunately, yours fell into that inbetween area, where it isn't working perfectly, but isn't to the point of qualifying for an exchange.
As for not being able to reach a manager, oftentimes they get very busy and are unable to return calls... so the sales associate will see what they can do to fix the situation.
My suggestion is to keep watching the bed to see if it does degenerate to the point of being covered in the warranty to be switched out. I do hope you sleep better on the bed and can understand why things weren't able to be worked out the way you hoped.