Yeah personally I think stress and the associated hormonal release actually plays a bigger role then most of the other things. In a way, it kind of closes up the cycle on itself (stress -> skin issue -> stress). However, there is surprisingly little research in this area. One study tried to link it to daylight and melatonine levels (source). While, another clearly states that emotion plays a large role in disorders of the skin (source).
This one is rather easy reading, but mainly it's just full of general observations. Interesting ideas are presented though.
One thing that really stood out to amongst the stuff I've been reading was that seborrhoea is actually not feature of seborrheic dermatitis (source). Might sound confusing, but basically the study demonstrates that seborrheic dermatitis is not the result of excess sebum production. In a significant amount of the patients, sebum production was actually reduced.
As for your questions. Not sure if the restoraderm would have any negative effect on acne. To be honest, never really had issues with acne. However, I don't think it should as they make lot's of cleansers that are suppose to help with acne.
Yeah, not sure in terms of the l-glutamine. Didn't have this issue myself. Let me know how it plays out.
Great to hear that your seeing improvements overall though. Hope it resolves completely for you.
All the best and look forward to any updates.