Germany, the Netherlands and Sweden pay at a reduced rate, because they've been paying in too much and also wanted a rebate of their own. Otherwise, I don't remember the exact rate, has to be around 0.3 percentage points out of the national VAT or so.

It's still only a small part of the funding. The majority are direct transfers.

Another small part comes out of the tariffs at the common border (of which the Member States get to keep a quarter, if memory serves...)