It looks like you're mainly looking for opinions. Looking at the sample survey, I'd say you'll have some challenges. The first is that I don't see a lot of UX groups will well staffed front end developers. IMHO, that should be a requirement for a UX team, but, alas, I don't see it as much as I should.
Secondly, for rapid prototyping, people likely aren't unit testing at all, nor perhaps caring about fine tuning jQuery selectors. That usually falls onto the development side. Again, I think UX should be developing the front end code but usually that's not the case.
As for the sample questions, it appears that you are primarily looking to see if they are aware of basic jQuery optimization techniques (selector specificity, element caching, etc.). Good questions, for sure, but likely not a primary focus of UX (again, even though it should be).
Finally, there are aspects of front end development that may appear to be a performance hindrance for the end-user, but offer internal development performance increases, which, in turn, can be a benefit to the end-user. I suppose it could be called pragmatic performance tweaking.
For instance, I will often traverse up and down the DOM to build a jQuery interaction rather than using strict IDs for each element and passing it into the script to make it easier for our non front-end devs to implement and reuse. A slightly slower browser experience (though admittedly perhaps imperceptible) but a definite boost to internal development speed.
UPDATE:
Xgreen, thanks for cleaning up the original question. To add some more specific answers:
Question 1: The individual designer perhaps does not need to be a front end developer, but front end development is a core component of the UX team's toolset. I've found that UX teams that do not do their own front end dev, or at least front-end prototyping, their solutions tend to be dated and not leveraging the full range of technologies and techniques available to them.
I also find that it's simply impossible to design every detail of every interaction on paper only. You really need to get into code to fully understand the entire user experience and adjust as needed. To fully design the user experience, you need to build it.
Question 2: This is a tougher question to answer. See my answer above. There's a lot of 'well, it depends' with this one. Both real and perceived performance issues are important to address within reason.