#4: Not Schwyzerdütsch, I think. On my reading, «bis»-Strich and zu Bindestrich are synonyms. If so, I would have used only one term, and if the latter, I would have written «zu»-Bindestrich, which I think is clearer.
#OP: I think you have to translate freely and write something like:
Ranges (text requires "to", digits require a dash)*
Use "to" to separate values which are given as text (e. g. "one to two months"), but a dash without spaces to separate values which are given as digits (e. g. "13–20 months").
*The alliteration of text requires "to", digits require a dash is a pleasing coincidence which makes the rule easier to remember.