1) Although I'm not planning to leave the school any time soon, I don't think I could use any of the information from these evaluations as "evidence of teaching effectiveness" if an advertisement requested that I send such information. At the very least, I think it would look unimpressive.
Evidence of teaching effectiveness can be demonstrated in a number of ways, including syllabi, course materials, peer evaluations, teaching awards, etc.
When/if you go on the job market, you can send the course evaluation summaries and note that there were three response items.
2) I don't think these evaluations will be useful in terms of any personal assessment I do for myself.
Two suggestions here: First, have someone you trust in your department come and evaluate your teaching. (Or many campuses have an assessment office that will come and evaluate your teaching.) Second, do a mid-semester evaluation with your own questions. You can have students provide typed responses to open-ended questions (assuming that you give them the questions in advance).
When I've done this, I've found it to be much more valuable as it allows me to make adjustments (or reset expectations) during the semester itself.
3) I'm a bit concerned about the fact that the first question addresses how often I cancelled class. I developed a medical problem this semester and canceled class once and there were a few times I let the class out a bit early...
I wouldn't worry about one question nor would I worry about one semester in which you had a health problem. When I evaluate candidates on a SC, I look for themes across semesters.
The response options require the student to indicate the number of cancelled minutes, and hopefully the students won't add up all the minutes they were let out early. I do put a lot of effort into making my classes productive and engaging and got high evaluations on questions assessing those aspects of my teaching at my previous institution. So I figured if I add questions about that and got good responses, it might cancel out anything negative about the "canceling class" issue.
It seems like you had a tough semester, but you also seem really defensive. Have you gotten other feedback (directly or implicitly) that you are already under the microscope?
If students comment, I suggest writing something in your self-evaluation (if you have one) about the medical issue if students comment on how early you let them out of class.
I wouldn't add any other questions, unless the form specifically allows you to add them.