If Italy leaves, that would indeed be the end of the EU, but I doubt they will really do it. They may leave the euro and that would also be a problem for the euro, but that may be overcome. Europe is facing many crises now and it will be difficult to predict which one will be the worst.
The British paid, but not as much as the Germans, so the impact on the budget will not be extreme. As long as the Germans stay in, and they see the benefits still, it will be ok. The EU is problematic, but many people also realise it is the only way for Europe to remain standing in a troubled world.