A nuovo record headset has a total stack of close to 40mm. Since you have 40mm you have nothing to worry about. You can use almost any headset you want and add spacers if you need them. 40mm is on the higher side for stack.

The lower cup stack is important for frame builders so when the design the bike they know how much height to add between the steartube and the fork crown in order to preserve the exact geometry they want. In practice many frame builders will just use a nominal number like 13mm as one or two does not make a difference anyone can see or feel. But in the current era of ultra precision anal retentiveness people want to build to an exact dimension. I.e. forget about lower stack height, it is not important, you only need to be concerned with overall stack height which will usually be in the high 30s to 40mm.

In terms of functionality it is not worth the premium for the campy. Cartridge bearings are better because the cups will never wear out like a traditional headset, but a good headset lasts a very long time and if you ride your bike enough to wear out a tange levin than your drivetrain will have been replaced many times over and you will likely have repainted your frame at least once. I wouldn't spring for campy since the frame and fork are mismatched and it sounds like this is a rider, not a show bike. I would buy the headset with the look you like the best.

The 4J on your fork is probably a date code. I wouldn't think about it too much, just put it on and ride.