Hi Jason
A good place to start is by reading/studying 'The Beginners Guide to SEO' which can be found here on Moz http://www.seomoz.org/beginners-guide-to-seo
From your list of keywords, it looks like your target audience is Employers who are looking for new Employees ? This list of keywords looks like it has the Adwords competition index and local monthly searches ?
If so, those are very targeted keywords with little search volume, though likely to convert well.
I'd suggest considering some more generic search terms also, Employers do search on terms such as 'recruitment' and 'recruitment agency', so worth revisiting your list of keywords to incorporate some higher volume terms as well.
That's not to say it's better to target those before the more targeted & longtail, can be easier to rank for those before trying the more generic, which can be supported by the longtail.
As for how many words, as many or as little really, depends on what your website has to offer and who your target audience are. A combination of high volume generics and lower volume longtail could be the way to go, depends on your website's and businesses' objectives.
Each page within your site would ideally be based around one main topic, so one main keyword, supported by one, two or three secondary keywords. Each page should serve a specific purpose and add value based around that purpose.
It can be useful to try keywords that you're unsure about via Paid search to get a feel for volumes, CTRs and conversions.
Hopefully some things to consider there.
Regards
Simon