Roger's quite right. Compression testing is a dubious art at best - depending upon accuracy of gauge (usually poor), seal to head, cranking speed, throttle butterfly position, amount of oil floating around in ring area, engine temp, etc etc.
Your readings are all about same so that's good. 15 bar is high!!!
If head gasket had gone a cylinder would have water in it when you started up and you'd have an instant misfire. Steam from the exhaust is normal - condensation burning off.
Does it tick over good when cold and when hot? Is the misfire only when revved or does it clear when revved?
If it misses on tick over and clears when revved I'd be thinking an exhaust valve. If it gets worse when revved, petrol, electrical??