I can sometimes beta if the piece isn't too long (and sometimes even if it is). It's good to have more than one beta though, especially if you have me beta because I have some blind spots and I'm unreliable.

1) Google Docs is arguably the best choice.
2) It quite depends on personal chiuce. As long as it isreliable, it's fine.
3) It kinda varies. As the Wiki article states, it can be anything between a single, nearly empty room with a basic restroom attached (the original type of RC as in the TOS) to a full multi-room apartment. Do whatever suits you. I, for example, gave to my Agents an RC not too big but with enough furniture to make it a decent home, since they live in it.