The most likely problem was the bleach step, not the fixer or re-exposure time.

In B&W reversal processing, the first developer creates a negative silver image. The bleach must then remove that developed silver image, leaving only the remaining unexposed silver halide. After that, re-exposure and the second developer turn the remaining halide into a positive image.

If the bleach is too weak, mixed incorrectly, or used for too short a time, the original negative silver image stays on the film. Then when you re-expose and do the second development, nearly the whole strip darkens, giving an almost completely black result. Your note that you could still see image content before re-exposure strongly suggests the bleach did not fully clear the first-developed image.

So the first thing to check is your hydrogen peroxide/vinegar bleach dilution, temperature, and time. A short first development could also contribute, but the symptoms point mainly to incomplete bleaching. The fixer is unlikely to be the cause of an all-black roll.