I have a half of an inch slope in my dining room. what is the thickest I can lay this product to make my floor level.

I've leveled about a 1/2" over a 3' by 3' space ... used three layers ... let it set up/dry a couple of days between the layers.

DAP® Flexible Floor Patch and Leveler (RTU) is recommended a maximum single application thickness of ¼ inch. For thickness greater than ¼ inch, it must be applied in multiple coats, allowing each coat to dry completely between applications (approximately 6 hours to a hard consistency, assuming warm/dry conditions). Maximum (total) application thickness is ¾ of an inch. Coverage: One quart fills approximately 3 to 4 square feet at ¼ inch of thickness.