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You won't shoot yourself in the foot. I saw Matt Cutts comment on this once in a video years ago. The reasoning is that if you have hundreds of domains all registered in your name and on the same server, with little value, then yes Google will likely flag that as suspicious.

I have around 10 large personal websites for years that do well on the same IP.

If you can get an IP address cheaply and easily, sure why not. You'll be fine either way, though.

It's not a penalty, but rather an algorithm change.

I'd be interested in hearing about your link building / anchors. You came out on top in the end - broad keywords are better in the long run.

20 Miles is too insignificant to warrant the need for two separate profiles. If you planned on doing community outreach and the offices were in different states, that'd make sense.

Just put your main office in the address field and be sure to list the second address somewhere in the information page.

Yes this is a potentially significant problem. The easiest way to troubleshoot is to do the 'site:' command again, and go to the last page of results. You should be seeing pages that aren't in your sitemap. Very likely duplicated content.

If you are having a rough time troubleshooting, post a link and I'll be glad to take a peek.

I've never understood the argument that category pages should be noindexed. They have always been an excellent source of traffic for me, too.

It's said that it could be considered low quality content. If you treat your category pages as just another page in your website (a healthy category introduction/description does wonders) it can be a nexus for broad search terms.

As an example of where this works very well, I have one category in a computer networking blog I have about TCP/IP. It's part of a series that explains the protocol, and the category page essentially is the 'guide' page, linking to each step in the guide to learning TCP/IP. I have the excerpts used only in category pages, so each category page also has unique preview content for each post.

Your specific worry is that you have posts in multiple categories. The thing is, there won't be the same posts in every category page so there will be a mashup of content. Some duplicate content is not bad. In addition to the category description, you'll be fine so long as you don't have synonymous categories.

You're fine in keeping them indexed. I would think you are crazy if you did otherwise