The nomenclature of mineral acids

My basic knowledge about nomenclature is: A mineral acid is called hypo when it has one less oxygen than the original one,

• a pyro acid when 2 molecules of acid add up with release of $\ce{H2O}$


• a meta acid when one molecule releases $\ce{H2O}$ and


• a per acid when it has one extra $\ce{O}$ in the structure connected with a peroxide bond.
  

  Question 1

  
  

  I was taught in my class that this structure:

  
  

  
  

  
  

  is correct because when we are drawing structures of a hypo-,per-,meta- or pyro- oxyacid, one must try to maximise the covalency.

  
  

  Why is that so?

  
  

  Also, usually in pyro- acid we find a $\ce{M-O-M}$ bond where $\ce{M}$ is the central atom(s). Like $\ce{P-O-P}$ in pyrophosphoric acid as show below:

  
  

  
  

  
  
  

  Then shouldn't the structure of pyrosulfurous acid be like this:

  
  

  Why is the structure not similar to pyrophosphoric acid?

  
  

  Question 2

  
  

  We know that in hypo-acids, there is one less $\ce{O}$ in the empirical formula of the acid i.e. Hypophosphoric acid should have one less $\ce{O}$ than in $\ce{H3PO4}$ i.e. it should be something like $\ce{(H3PO3)_$n$}$. If we put $n=2$ we have $\ce{H6P2O6}$.

  
  

  
  

  
  

  But why is its formula $\ce{H4P2O6}$?

  
  

  I might lack some information about it or maybe I've understood the concept wrong. Please help.