Meaning of 所 in "有所..."
As you had said, 所 is not redundant. But to me, "有帮助" and "有所帮助" doesn't have that much differences, especially when you are in an oral conversation with Chinese people.

As for your explanation for "有所謂", the translation for "这件案子有所谓" is "This case matters." You are correct. But I don't think that it has the meaning of "has something that it says". Yes, "謂 = 說". However, the literal meaning of this is not strong when you say "有所谓". When hearing about "有所谓", please just take it as "matters", and just forget about its literal meaning.