Firstly I would like to say that the O.S 32 would have to be one of the most forgiving and easy to set up model engines that have put one the market. The reason for me saying this is that your problems may be more due to model set up rather than the engine itself.
As far as the leaking fuel goes it could be for a number of reasons. Fuel may be spitting out of the carb while the model is running and finding its way to the ground via the head. Ive seen this happen on a blokes heli and it was fixed by putting an air filter on the engine.
Fuel could be leaking out of the head but as long as the bolts are tight this would be unlikely. When tightening the head bolts make sure that you tighten opposite bolts rather than just going arounf the head. Tighten them a bit each pass so that you reduce the chance of distorting the head and inducing leaks. Also make sure that you are using a glow plug washer.
The engine should not be over reving wildly like you have explained. If it was reving to say 30000 revs you would have a head speed of around 3500 which would be good for the ultimate 2 second tic toc but thats about all. Sounds to me like like you have a clutch problem which is allowing the engine to overspeed.
You really have to get an experienced modeller to have a look at your set up as this kind of over speeding will destroy your engine.
Hope this helps,