I am in the process of formatting the samples for RenderX XEP.
I got problems with three of your files - I believe they contain 
errors. I attach validation messages that seem to render the XSL 
FO instance invalid. 

Sample1.fo: see Sample1.err.log

Sample3.fo: see Sample3.err.log

Sample4.fo: I am concerned with the use of  keep-together="always". 
   By the XSL Spec, keep-together is a shorthand notation that is 
   equivalent to setting three components to the same value:

       keep-together.within.line="always"
       keep-together.within.column="always"
       keep-together.within.page="always"

  The first conponent effectively disables all line breaks, constraining
  the contents of the whole block to a single line. I believe there is an error
  here: the intent of the author seemingly was to disable page breaks only.
  I believe this attribute should be given an explicit component specifier:
  keep-together.within.column="always".