1) I think you don't need to say ":554" if you're using VLC -- that's the standard RTSP port, and I think it looks there by default.
2) That only works if you're on the most recent firmware. Are you? (See the PCTV To Go downloads page, and compare the version # there with the version# in the setup wizard).
3) No idea how to "embed" this into your website. Never tried it, here. I think you'd need some sort of player on the viewer's computer -- MAYBE an appropriate Windows Media Player can play RTSP (dunno), or MAYBE some sort of high-powered Java applet, but you're on your own to figure that one out.
I just got the PCTV To Go to place-shift my video. I've never tried messing around with streaming...that might be better served by another, better-supported product.