Re: derisory renegotiations
The 54% is for National Parliaments. Sadly it's basically a non-event - though it gives legal force to an exisiting system, where if enough parliaments get together they can forced the Commisison to reconsider a measure they don't like.
In normal Qualified Majority Voting - which is what happens in the Council of Ministers (when they're not doing it by unanimity) the blocking minority is something like 35%. Both voting systems are done by population, So Germany, Britain and Poland together are a blocking minority in QMV.
For the Parliamentary red card, I think that means if the British, German, French and Italian Parliaments were to get together, they could block any Commission regulation. Of course that would mean Parliaments defying their governments, so it's sadly a good idea watered down to be mostly ineffective.