Example URL:

http://cdn.seomoz.org/q/help-with-getting-no-conversions

Canonical is a RELATIVE link, should be an absolute link pointing to main domain: http://www.seomoz.org/q/help-with-getting-no-conversions

<link href='[/q/help-with-getting-no-conversions](view-source:http://cdn.seomoz.org/q/help-with-getting-no-conversions)' rel='<a class="attribute-value">canonical</a>' /> 

13,400 pages indexed in Google under cdn subdomain

go to google   >  site:http://cdn.seomoz.org

https://www.google.com/#hl=en&output=search&sclient=psy-ab&q=site:http%3A%2F%2Fcdn.seomoz.org%2F&oq=site:http%3A%2F%2Fcdn.seomoz.org%2F&gs_l=hp.2...986.6227.0.6258.28.14.0.0.0.5.344.3526.2-10j2.12.0.les%3B..0.0...1c.Uprw7ko7jnU&pbx=1&bav=on.2,or.r_gc.r_pw.r_cp.r_qf.&fp=97577626a0fb6a97&biw=1920&bih=936

I would not remove the H1 tag. Its only one of many factors in rankings but it's still important. Don't do anything shady with it just show it. It doesn't have to be huge default

size you can style it you know.

You should bucket the categories into 10-20 primary categories. If you have have lower level categories that are potential traffic drivers, you can feature a few select categories along the primary categories. Every link takes away Pagerank from the host page and too many links on every page will devalue the pages. It's hard to give clear directions without seeing the site,

I don't know what you mean that users don't see the links and Google does. Are you hiding links? That may penalize the site.

Minimum of 500 words on a page. If the page is informative and not repetitious you can make it as long as you want you'll never get penalized for adding too much good content. Some wikipedia pages for instance are extremely long.

But the reality is if you're not a site with user generated content

a) who's got that amount of time to dedicate to every single page

b) overly wordy pages on a commerce site kills conversion rates

c) chances are that much content could be broken up into a few pages which all target different keywords better

That is really good advice, i think the missing piece that we don't know in order to recommend the best approach is how much are these landing pages promoted on the web and are people linking to them. It all comes down to whether you are throwing away PR or not.

If a LP has good links pointing to it i would 301 it, if the LP has only a couple of links pointing to it, the slow 200 then 404 is a good approach.

"if a tree falls in the woods and no one is there does it make a sound?"

"if a page 404's and no one is linking to it, does it 404"

in other words, if there is no internal linking to the LP on your site and no one is linking to it and it is not in your sitemap xml files then you can simply remove the URL in WMT and Google will not report it as a 404.

I would 301 them to the homepage or if you have a main directory landing page that lists all of the offers. You don't want to 301 them to the closest landing page offer because that one too will have a limited life and you'll wind up daisy chaining redirects. Google has no problem with a site having a lot of 301's.