Got to admit that I don't have an answer for you right away and I'm not completely sure what you're trying to accomplish. I don't believe "smashing two things together" is something SSRS excels at. It has no "glue"-ability or grouping features (outside of a rectangle). It has no way of relating two unrelated result sets together.

Perhaps your answer lies in your dataset? "smash" your rollup queries together in your dataset then simply display the results in SSRS. The dynamic nature of tablix objects makes them difficult to align with other objects, even within a rectangle.

As far as the report looking different in report manager vs preview in your data tools, they render differently. Hidden fields can sometimes create havoc in IE, but it's mostly just because they render differently. At least in BIDS 2008R2 they did.