and balancing on eyebeams above a sea of faces paces his way to the other side of day (9-12)
The poet-acrobat's biding his time on that high wire, not just for the sake of his performance, but also for the sake of his life and career. The audience's eyes are like balance beams, forcing him to have a steady hold on the art he's creating while not letting himself feel overwhelmed by that "sea of faces."
before the taking of each stance or step in his supposed advance toward that still higher perch (22-24)
Each step matters, and these "steps" are really just symbols for the words and ideas a poet may use. And it's only a "supposed" advance, suggesting again the uncertainty of everything he does. But he sees that perch, and he knows if it's there, he can reach it. He can catch Beauty.
a little charleychaplin man who may or may not catch her fair eternal form (29-32)
Our poet-acrobat is unassuming by this point, both in appearance and purpose, and is vulnerable just like the rest of us. There are no assurances, just Beauty's "fair eternal form" waiting to be caught. But hey, things could be worse. Imagine if there was no Beauty on the other end. Then he'd certainly be doing more than just "risking" absurdity. He'd be risking utter failure.