1) Put the palm of your hand over the end of the exhaust pipe...if its blowing you'll hear and feel exhaust gas escaping.
2) An oil leak in the timing belt area is bad news as it can cause the belt to fail prematurely.....try and trace the leak - check the oil filter as well as any breather hoses in the engine bay, particularly in the rocker box area.
3) The brakes are slightly binding, causing the squeal....they need to be stripped down, cleaned or replaced as necessary, and copper grease applied to the back of the pads
4) You still have a wheel balance problem, but it could also be due to a deformed tyre or buckled wheel rim.
John
August 2009