My question is how to most efficiently set up crawling of 3 web sites.
We have profile 1 = our site 1 + external site
we also have profile 2 = our site 2 + the same external site. Is that the best setup (to crawl the same external site twice) or can we set up the external site as a third profile, crawl once, and somehow copy the data to the existing 2 profiles?
No time. If the regular profile searches are working a meta search of those profiles should work immediately. Make sure you've set the "visible" flag under search settings for the regular profiles though.
You can use any IP or name that the appliance can resolve to the proper machine. But in the case of a single appliance meta searching itself you'd generally use "localhost" or "127.0.0.1".