Well, you accomplished what needed to get done but in a way I didn't think of. By checking voltage between terminals B+ and DF at the regulator and generator, you've determined 3 things; 1) there's battery voltage at the B+ terminal (that's good) 2) the DF wire is OK (also good) and 3) there's no voltage at the DF terminal; not good.
Please keep in mind that due to the lack of popularity in the use of generators these days, my diagnostic technique IS rusty. This next test is used to test alternators so it may work for generators too. It bypasses the regulator and applies battery voltage to the field circuit. Hence the term 'full fielding'. Hook up the voltmeter to the battery. Start the engine and run it at a fast idle, say 1200 - 1300rpm, using the hand throttle under to dash (so THAT'S what that thing is for
). Note the battery voltage. Momentarily jump terminals B+ and DF at the regulator while looking at the voltmeter. If the voltage stays the same or drops, the generators not working. If the voltage increases, the generators working but the regulator isn't.
The only difference between the part number on your generator and what's listed in the parts book is the '0059' which isn't in the parts book. What is listed though is the letter (R) in parenthesis after the 'EG'. The Bosch regulator # is 0 190 350 023.