>   a) make a particular channel or network/channel tab current;

For this, you can use:
    set_context(nil, SERVER_NAME) #where SERVER_NAME is the name of the server tab, for example, FreeNode. Use find_context to get a specific context to use for this
    command('JOIN #channel_to_join')

That will make the server tab you want the main focus, and then calling JOIN to a channel tab you already have open, will make the tab the main focus for the GUI.

>  b) send text (think self.puts for now) to a particular tab;

To do this (assuming you mean to send text to the channel) you have two options:

1)
    command('SAY ${ text }')

    The limitation with this method, is that there is a limit to the length of text that you can send. The way to get past that, is to use number 2.

2)
    command('MSG ' + get_info('channel') + ' ' + text)

    This is still limited to the IRCd's text receive limit, but you are no longer restricted by the SAY's limitations.

And to make these work correctly, you must use set_context as described in my first answer.

> c) send text specifically to the/a server tab for a specific
>   network.

To do this, just set_context(nil, server_name) like in the first example, and then use:
    command("COMMAND_NAME ARGS")

For example,
     set_context(nil, 'freenode')
     command("MSG #channel Hello!")
would send the message, 'Hello!' to the channel #channel, on the freenode server tab open in the client.

Once again, I hope I have helped you :) and I don't regret it at all, I'm always happy to help.  As usual, contact me with any further questions.