"
specify --dst yourself" is the important line to note
If you know which device is the disk you want to wipe (it should not be a removable disk), specify it carefully using the --dst option
If you didn't get a live session though, chances are not good that anything desirable will result from installing the system onto the hard disk. (In other words, the USB is indeed supposed to boot to a live session. You should have seen "chromium" boot screen, followed by wifi selection prompt and login screen... if not, your hardware is either not supported or not well supported.)
Yes, 12 partitions is normal. ChromeOS has a complicated GPT disk layout to make automatic updating stateless and easily revertible.
I tried this myself today, with a Thinkpad x220, I had good results after installing ArnoldTheBat's "Special Build" -- working wifi, sound, power management, some quirks updating (it seemed to try updating every time I checked for an update, stuff broke, until I followed the instructions completely and issued a "stateful_update" command... that seemed to fix it) -- no graphical problems with the special build, except for immediately following an update, when the system glitched out a bit and crashed on me.
I tried with the nightly build for amd64 after, and predictably, I was not able to get on any wireless networks (no linux-firmware package in the nightly build, just stock chromium os). But overall, it seemed to be working except for that.