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Nothing is set in stone as far as number of times a keyword should be used. Although from experience I find 5 or 6 is more than sufficient.

But Mike is certainly correct up front for title and H1 and that would get you off to a good start. Other areas to pay attention to would be making sure you don't have conflicting or too similar keywords in your text also.

Recently saw a paragraph with 15 keywords and probably the same amount of synonyms of that keyword bunched into a few lines.

We worked in partnership with a similar large scale site last year and found the exact same. Google simply cut off 60% of our pages out of the index as they were cookie cutter.

You have to ensure that pages have relevant, unique and worthy content. Otherwise if all your doing is replacing the odd word here and there for the locality and job name its not going to work.

Focus on having an on going SEO campaign for each target audience be that  for e.g. by job type / locality / etc.

Following on from NoahGlasers comment.

Use the disavow link - however we used it on a new SEO client we picked up recently and so far its done nothing for us at all. We are trying to clear up their spammy link profile to.

That said I have seen disavow tool bounce back sites that dropped due to overly spammy link profiles outweighing good links.