So, the holdup (aside from having very little idea what I am doing) is that when I attempt to write data to the I2C bus, I get a Remote I/O Error, meaning I am not recognizing the device with which I am attempting to communicate.
What I just realized this morning, however, after noticing the slight detail of the Read bit being set on the observed communications, is that I've been picturing this whole situation all wrong. Because the sensors are SLAVES on this circuit, and the controlling chip is the master, which means it is READING data from the sensors, whereas I have been trying to _write_ data from my Pi.
So, clearly, the trick is I need this controller to ask me for data so that I can respond to it, not try to initiate a conversation on my own. There must be a signal being sent whenever anyone touches any part of the sensors, which triggers the controller to send a request to address 0x53, and read back the current condition of the sensors.
However, that's about as far as I have gotten. If anybody stumbles by who has been down these roads and has advice for me I would be all ears!