Thank you for your questions. I would like to answer them in reverse of the order in which you asked them.
First, in response to your question #3: It is true that the Guidance states Nemeth symbols are not to be listed on the special symbols page (SSP). It is also true (and the upcoming changes to the Guidance, which are introduced nicely in Dorothy Worthington's webinar from 7/20/2017, clarify this) that the "opening Nemeth Code indicator" and the "Nemeth Code terminator" are UEB symbols and should be listed on the SSP according to braille order. Also, it is recommended that the "Single-word switch" Nemeth symbol be listed on the SSP, under its own heading (e.g., "Nemeth Switch Indicator") because it is new but not a UEB symbol.
In response to your question #2: I agree with your view that within a list or series of short exercise items it is disconcerting to have an opening Nemeth Code indicator placed on a line by itself. What I would do with such an indicator is to place it after the item identifier, just before the affected material. For example:
In response to your question #1:
You're right that it is preferred to use fewer instead of more Nemeth switch indicators. Still, it is of course our overarching goal to make the text as clear and intuitive as possible. So, if having a few more switch indicators makes the content more readable, then those switch indicators are well used.
I agree that the first two options you provided in your question #1 are both correct. I would argue that the second (lines 07-10) is more reader-friendly, because it allows each item to be read individually (i.e., the content of item #26 is not dependent upon a switch indicator that is within item #25). I cannot say that the third option you provided (lines 13-16) is incorrect. Nonetheless, allowing Nemeth Code to remain in effect for a series of unmodified numbers and/or letters is possibly overextending application of the Nemeth Code.
Finally, if you did have something like
- Nikola Tesla
- 1 G = 10−4 T
where one item/line of UEB material occurs between items/lines Nemeth material, I would suggest terminating Nemeth Code at the end of item #23 and then inserting an opening Nemeth Code indicator following the item identifier "25."
Again, thank you for your questions.