In my opinion there are too many variances in salaries and standard of living across the EU to provide a common welfare system, how some of the countries have passed the tests is beyond comprehension....Greece for one should never have been allowed in based on their fiscal position.
The western countries are too generous in terms of benefits and it is little wonder so many from the eastern EU countries (and many NOT even in Europe) either want to come to the western countries for benefits.....before anyone kicks off, I am not referring to those who work and pay taxes...I am referring to those who gain benefits or credits of some sort...housing, child etc.
The tax payers can no longer afford to pay for these across the EU, yet the Officials want to invite even more countries who do not/cannot and will never comply to many of the rules set, but hey, Merkel et al want them in...
Not answered all your questions but this will stimulate some debate.