I wish I could help you, francspenser, but I'm in the same boat. I have almost a full grid, with only 3 unsolved clues in the NE corner. I have all the extra letters apart from the one from the first word of the title (though I'm not completely certain about 2 of them), but I cannot make any sense of them at all. I cannot work out what the first word of the title might be. None of the possibilities I've got so far looks remotely likely, nor does the second word, which could be one of two English words or one of two German words. The thematic treatment of answers to clues with normal definitions clearly involves jumbling, but I cannot see anything systematic; I assume there must be a system to avoid the ambiguities of some entries such as 35a.
I have noticed that the letters of the second word of the title seem to be replicated, though in different order, in the last few extra letters from the numerical definitions, but it's significance escapes me. I have also followed fyellin's advice re 26A but I'm still in the dark.
Looking at the very small number of comments so far my guess is that a lot of solvers are struggling. I wonder if BeRo is aiming for the lowest number of entries for this year.