Thanks Chris
6D: I (stupidly) kept seeing the single letter for Everyman, rather than the alternative. Still don't understand what 'needing healthier' is doing in the clue though. And it definitely should be spirit (sing.).
19D: As you say, German would make more sense, and the other single letter abbreviation is another one that has passed me by (c.v. 26A).
26A Yes, 'therefore' is a better synonym so it's a mystery why the setter didn't use it. As far as I can remember, that particular Jack came down the beanstalk, too. There's an actor called Jack North (thanks Google), but I suspect he's too obscure even for this setter. Maybe we should think of jacking up a car? (Although, again, I reckon a car is jacked DOWN once the tyre has been changed!)