For the page breaks select the column in the Row Groups section (bottom left of the designer window), then expand the Group property then PageBreak. Add an expression using the RunningValue command in the Disabled property to evaluate into whenever you want a break such as:

=iif(runningvalue(fields!ID.value,count,"enter tablix control name here") mod 20=0,false,true)

For the repeating headers try right click the row, Tablix Properties, then Repeat header columns on each page.

That should do it.