Well, rel=canonical will technically work fine, however in this case if you are migrating the entire site (presuming you have all pages on the old domain, going somewhere on the new domain, I would essentially setup 301 redirects from the old domain to the new domain.

I don't think you should do anything in the webmaster console. Just remove all the pages from the old domain and setup 301s from old domain to new domain. Google Webmaster Console Site migration IMO is for scenarios like you have yourdomain.net and you acquire the domain yourdomain.com and want to migrate the domain from .com to .net or if you change the brand name to yourbrandname.net or so on.

Does that make sense ? I hope that helps.

I understand your concern. I am basing my answer based on the fact that if you don't have a robots.txt at all, Google will still crawl you, which means its an allow by default. So all that matters in my opinion is the disallow, but because you need an allow from the wildcard disallow, you could allow that and disallow next.

Honestly, I don't think it matters. If you think the way a bot would work, it's not like robots.txt 1 line is read, then the bot goes crawling and then comes back reads the next line and so on. Does that make sense ? It reads all the lines in the robots.txt and then follows the directives. But to be sure, you can do either of the scenarios and see for yourself. I am sure the results would be same either way.

I don't think it matters, but I think I would disallow first, because by default everything is an Allow.

Yes, as Ryan said, this is the nature of the internet. Just like you can write about anything, anybody, you can create a link to anybody and just to clarify, the block that Ryan is talking about is essentially that if someone linked to you, you could "technically" setup a block so anybody visiting your website from that link, would not be able to access your website..but it would still get counted as a link from that website to yours.

Yes, no need to be worried. You are good. rel="external" is the XHTML valid version that informs search engine spiders that the link is external. However, using this does not open the link in a new window. target="_blank" and target="_new" does this, but is not XHTML valid. I hope that helps.

The robots.txt would probably not be a part of the Wordpress Configuration. Allow indexing is controlled via Meta Data by the Wordpress Architecture.

I would look for something like this in yourdomain.com/robots.txt

disallow /

or something like that. If that does not help, PM me your site URL and I would be glad to look it up for you.

In that case, I would not sweat over it. If you think about it, companies can't control who links to them. Imagine all those Wordpress, Blogspot Blogs, which have a sitewide blogroll. If a mommy blogger created a blog 5 years ago and linked to Disney.com for example, and now she does not even remember that she created a blog...what can Disney.com do about it and they are all from username.wordpress.com kind of URLs, so all from the same IP.

Anyways, long story short, all kinds of links...add up to become a natural link profile. For Web Design companies, this is fairly common in my opinion and good news is that you are using brand as a keyword, so I don't think there's something to be worried about. Going forward, if I were you, I would nofollow the links. But leave the old ones as is unless there's an issue in which case you could add nofollow to those existing links as well.