You've got the general idea
It's a great idea to ask users what they dislike and then to set about proving them right or wrong by conducting a usability test before you spend resources fixing the perceived problem. Users often complain about a symptom without recognizing the underlying design problem.
If this is what you intend to do, then your survey is a good step forward. (I'm leaving it to others to comment on your survey design.) If this is not what you intended to do, then please read on.
Typical usability testing
Typically, you would have a specific feature in mind that needs testing. If you don't have a specific feature in mind, then you might want to determine their goals—so what users do on the site. You could infer this by looking at site traffic, log data ("analytics"), by asking them, and so on. You might also ask your Product Management team or your Marketing team what their goals are for the site.
Note that "asking them" could involve a survey.
Then you would develop scenarios that require users to complete specific tasks related to those goals. After screening and scheduling your participants, you would observe and measure their performance. Or, if you use automated testing, you would allow the system to gather data that you review.
Your analysis of user performance will reveal the usability problems. This would result in recommendations that you prioritize. This typically considers cost to fix the problem, seriousness of the problem, and the company's marketing focus and Product Management goals.
A bit of reading
Here are some articles you might find interesting.
I hope that helps you move forward.