How did attitues to the deutero-canonical books in the Western Churches change during the second millenium? What was the pre-Reformation understanding and how did that change during and after the Reformation Era for Protestants and for Catholics? What is the current position?
Current Position of the Roman Catholic Church

The current position of the Roman Catholic Church is given in Articles 135 and 138 of the Catechism.


  
  The Sacred Scriptures contain the Word of God and, because they are inspired, they are truly the Word of God. 
  


and


  138 The Church accepts and venerates as inspired the 46 books of the Old Testament and the 27 books of the New. 


So the Roman Catholic Church teaches that all 73 books contain the Word of God, and are the Word of God.

Pre-Reformation Position

The attitude of the Church to the 7 books, known as the Deutero-Canon, was that they weren't necessarily equal to the other 66. The Catholic Encyclopaedia has this to say:


  In the Latin Church, all through the Middle Ages we find evidence of hesitation about the character of the deuterocanonicals. There is a current friendly to them, another one distinctly unfavourable to their authority and sacredness, while wavering between the two are a number of writers whose veneration for these books is tempered by some perplexity as to their exact standing, and among those we note St. Thomas Aquinas. Few are found to unequivocally acknowledge their canonicity. 


They were certainly part of the Bible, but their status was somewhat doubtful in comparison to the rest. The Encyclopaedia goes on to say one reason was the prominence of Jerome's opinions in the Ordinary Gloss, the widely used  medieval commentary.  Richard Field , former Dean of Gloucester, wrotegiving a translation of part of the preface to this:


  Many ... suppose that all those books bound up in the Bible are to be in like sort honoured and esteemed, not knowing how to put a difference between books canonical and not canonical. 


There is a 


  great difference as there is between that which is certain and that which is doubtful.  


and 


  they that are not canonical are very good and profitable but their authority is not reputed sufficient to prove the  things that are questionable.


This is the point of view which educated persons in the middle ages  read.

Reformation Era

During this period people ceased to regard the 7 books as of doubtful authority. They made their minds up.  Protestants decided quite definitely that they are not authoritative, and Catholics (Council of Trent) decided quite definitely that they are.  (Of course, each claimed to be merely reasserting  ancient understandings.)

After the Reformation both Protestants and Catholics agreed that there were 73 books in the Bible. The difference was that Catholics held all alike and Protestants did not.

Luther, Calvin and King James etc. did not remove the books from the Bible. Luther collected them together in a separate section of the German Bible, a practice followed by the translators for King James (the First and Sixth). This was to assist readers in identifying inspired and uninspired parts of the Bible.

Subsequent to the Reformation

Many Protestants did as described in the first B> in the question. They decided rather than have a 73-book volume containing 66 books regarded as the inspired Word of God, and 7 books which were not the inspired word of God; that it would be better to have a volume consisting solely of the inspired Word of God.  They started printing copies of the Bible which contained only the 66 inspired books. Almost all modern printings of the King James Bible, and most modern Protestant translations, leave out the 7 books altogether. 

Summary, in the form of the  Question

Pre=Reformation: We have 73 books but we're not all  100% sure about 7 of them. 

Reformation Protestants: Actually, we are sure, the 7 definitely aren't inspired. 

Counter-Reformation Catholics: Well, we're sure they definitely are.

Some Post-Reformation Protestants: Hey, wouldn't it be nice to have a book that just had the inspired Word of God. 

Other Post-Reformation Protestants: good idea, yes,  lets  leave  the 7 out.

Needless to say, like all history, it was much more complicated than this, but I hope this gives a general overview.