1985 BMW 318 Ignition timing

Engine Mechanical problem
1985 BMW 318 4 cyl Two Wheel Drive Manual

My 85 318 had rust in the entire fuel system when I got it I have coated the fuel tank, replaced both fuel pumps and replaced injectors. It already had a new distributor wires and plugs when I bought it, now that it is running it idles at 1000 rpm and runs rough up to around 3000 rpm. I suspect a bad O2 sensor but my question is how do I check the timing with a timing light, I know the dealer uses a sensor in the flywheel housing but I dont have one and aint gonna buy one. I also know there is a pionter on the front cover and 2 marks on the dampner if they are used which mark do I align with the pionter. Also my book says there is a ball on the flywheel but I have yet to find it all I see is the tdc marker. It also smokes some of that may be oil but not sure
Any help would be great