Good news, Peter!
By following your instructions to the letter I was able to get the game going in the nav tutorial under a new career name. All the controls I tested worked so far, but I haven't yet given the boat a thorough wringing out. Just enough to get my face wet and come back to report.
The only mods in the [German] JSGME are the main LSH mod and the HSIE patch. As the game loaded the screen read: GUI [4:3] loading, which I interpret to mean the screen ration is 4:3. The display takes up the entire screen, which is 17" or 17.5", can't remember which off hand.
Once in the game, past the initial loading screen, I see "Loaded by LSH3 Commander 2015 v. 1.6b1
Which looks like success to me.
If I cannot get any further progress than this, I will still be a happy camper. However, now that I know I must load via Commander even for testing purposes, I will now try to enable a widescreen GUI and use the same procedure.