I always interpreted him to be a sort of foil to Hojo - a scientific genius who was more invested in giving back to the Planet for the sake of all stakeholders.

As for hearing the Planet's screams, I pin it on the observatory; it seems like his observatory machine is not just a model but can accurately depict universal events in real-time (like the comet in the FMV). With further fanwanking, one could say that since he built the observatory in order to observe the Planet, it is able to pick up on normally undetectable signals as the Planet screaming (i.e. the screams are essentially sets of data that can't be picked up without proper equipment).

About his legs… I've wondered the same thing myself. I always guessed that since he was so old, and such a great scientist, that he built himself a sort of hover-craft.

I seem to remember a scene where they hear the screams on the Highwind also. So I'm not sure about it being the machinery of the observatory, but perhaps once their ears had been opened to the planet that then they could hear it.

That's true. The way I took it is that the Planet's screams are usually inaudible without certain amplifiers such as the observatory. But when they hear it on the Highwind, the Planet had been damaged to such a point that its screams began to emit at a frequency audible to the unaided ear (ie. the Planet started screaming "louder" so to speak).

I feel like it wouldn't make sense for Planet screams to be audible in general because there is the implication that the Planet has been constantly screaming throughout the entire crisis - and it only is audible to the naked ear during that breaking point.

He isn't an ancient. His a person taht cares for the planet... a Cetra... then again the Cetra remind me of hippies.

Bugenhagen has been around a long time and probaly knows more than most people on the planet. it's odd that he floats though, and it's kinda funny