Bonus Quizzes to entice students to read their syllabus?

I'd avoid setting summative assessments (i.e. for course credit) on topics other than the subject material you expect the students to learn. Doing so might come back to bite you, even if you keep the relative contribution to a final grade as low as you are suggesting.

Perhaps you could spend half of your first lecture rhetorically asking the sort of frequently asked questions that get your goat, while at the same time navigating your course webpage, to show where a student will find the answer to your questions. After reading out five or so of the most commonly asked questions, the students will get the message:- the answer is likely to be on the webpage. Look for it.

As I'm sure many lecturers/professors would attest, one of the frustrations of teaching can be the continuous asking of questions that had a student read their syllabus and/or navigated the online learning site, would have most likely been answered.

Ha ha! Yes, it really happens all the time.

Regardless, I still receive countless emails and questions not about the content of the course, but [...] where my office is

My students typically wander at the opposite side of the university with respect to my office and when they eventually succeed in finding me, I ask them: haven't you read the location of my office on the syllabus on the course website? I let you figure out what the answer is...

Students simply don't read page-long bureaucratic information.

In speaking with a number of academics, some of the solutions have been creating assessments based solely on the syllabus

I don't like this idea nor that of bonus quizzes.

To solve this problem, this year I've decided to remove the syllabus altogether (no one reads it anyway) and to send updates by email to all the students (e.g. hey guys, the new homework is online and is due by etc.). Every email should contain just one piece of information and have a length of just a couple of lines. As for the office hours, they are by appointment and I give office directions when they ask for it.