Welcome to the Q&A Forum

I've gone through several large relaunches in recent years. I kept bullet point notes on what should be done to avoid ranking decline & wrote about it on my blog, hope it helps - http://www.andy-maclean.net/seo-website-relaunch-checklist/.

If results fell off a cliff, my 1st port of call would be checking the redirects were handled correctly, nothing untoward is going on with your robots.txt file and check GWT for any significant issues.

Andy

Dont know about theme but you NEED the Yoast SEO plugin for wordpress - it really is awesome.

No is the short answer. Having almost identical pages  with only minimal differences (for the purposes of SEO) is exactly the kind of spammy thing the recent Penguin & Panda updates are clamping down on. If you dont have stores in california, new york etc Google doesnt want to rank you for those terms.

PPC would be a better solution for those kinds of terms if they can get past the minimum search threshold.

Optimising product pages for types of hammers e.g. claw hammers is the way to go.

In the Google Places listing the 'categories' are mega important but under-used. If they arent using all 5 available categories they are missing out on serious traffic.

Most hotels will just have 'hotels' or 'self catering' (i forget the exact default options). Use ALL the categories to rank for more terms. If they need traffic pronto add 'spring break', 'mothers day' 'weekend break' 'last minute break' categories - you get the idea. This is an awesome trick I use for a holiday cottage client e.g. I use 'christmas break' 'easter break' 'dog friendly' and other out of the box terms as categories to keep pace with seasonal demand.

Note: Google will not always listings for ALL category entries, you'll have to try it and see.

Heres a relaunching a site SEO checklist I did a while back which may help.

The Penguin update as described by Google is to hit 'over optimized' sites. Creating duplicate pages with minimal word changes for the purpose of SEO is exactly the kind of thing that Penguin is for - so no, its not an easy opportunity, its not an opportunity at all.

No problem Paul, hope it helps, let me know if you have anything to add the list, ill credit it back to you.

Definitely not the sub domain. Assuming you're adding content to help rank well for additional phrases and to improve your sites authority this is best done using subfolders i.e. store.com/answers. You'll get more link juice to those pages keeping them on the root domain. Also any links you get to these new pages benefit the whole root domain i.e. store.com, which isnt the case with links to a sub domain.