Thank you for your question. As you know, there is not a rule for every problem, and I am happy to see you are approaching your work with the reader in mind. My answer is based more on my experience brailling in a classroom situation, and so contains a little bit of opinion.
When a tactile diagram is placed on a different page, I think it is a good idea to label such drawings -- not only does it help the reader, but it helps the person who is assembling the braille volume if the tactiles are stored separately. It could be there are guidelines regarding this in the new BANA tactile graphics text -- please check that document for guidance, too. I am not thoroughly familiar with it yet.
Regarding the two examples you posted, I agree with you that question 3 on page 5 needs direction since you are placing the graphic on a separate page. "Use the graph on the next page to complete the statements below." would work. At the top of the graphic page I would put "3. (cont.)" in cell 1. There is no rule stating this (again, please check "Guidelines and Standards for Tactile Graphics") but it is a technique I use in my work which has been quite helpful when compiling a volume, and it gives the student confidence that he/she is looking at the correct drawing.
For your sample page 6, rather than repeating the TN after each problem 5, 6, and 7, I would put a TN after the "Try This" instructions, something like "Use grid on next page for questions 5-7." Also, at the top of the graphic page I would insert a TN "Use with questions 5-7." Another thought would be to put "Try This (cont.)" as a continued heading at the top of the graphics page instead of the TN.
Thoughtful application of TNs and repeated headings is always needed -- you don't want to clutter up the braille with unnecessary text, but in this case I think they help clarify what is obvious in the print copy.