Maybe the chain and sprockets are worn and need to be replaced. As the chain stretches it wears out the grooves in the sprocket so eventually the links of the chain will not fit inside the teeth of the sprocket properly, the teeth of the sprocket the cut into the chain and this is often what causes a chain to break.
From what you say, it seems almost certain that your clutch slave (the cylinder mounted just in front of the front sprocket) has cracked. This is a really common problem because the slave cylinder is not strong enough. If you have a leak of mineral oil around the cylinder then that's it. It happens on every 950/990 in eventually.
There are stronger after market cylinders on the market, so you just replace the leaking cylinder with one of these and the problem is solved. If you search this forum you will find lots of info about the clutch slave.