A way to check difficulty
 

Is there any way to check the difficulty of a running game, inside the game or with a 3rd party tool?

You can view the end-difficulty, so the single rate 50% to 200%, by saving the game, and afterwards dying. I'd recommend flying into a dominator-system without any weapon, droid and shield generator.
Now you can check the difficulty in the results screen. Obviously you should load the game again afterwards, that's also why you should save ;)
If you mean the detailed list, I have to pass, though. Don't know a method.
Greetings
Silverman

Yes that seems to display the compounded difficulty, but it doesn't show the sub-difficulties.

If this is the current game then I think you can see the current sub-difficulties by starting a new one, it should keep the previous settings iirc

That only affects the new game, in this case I want to know the sub-difficulties of an old already running game. So that if my compounded difficulty is 150% I want to know what settings are in normal, hard or impossible.

Well, the only thing that remains or should remain unchanged for an older game are the save files. So if this kind of info is stored there and if there is an editor to read them maybe you can find it this way.
A couple of big if's but I can't think of something else atm, I've checked the game folder for any other file that could save this and didn't find any.