Hey folks. Let's answer these issues sequentially:
1. Keyword Density: No, this does not matter. Period. At most, another metric called Tf/Idf (term frequency over inverse document frequency) might matter, but this is old-school text relevance stuff that is no longer that valuable. For on-site, keyword location matters the most (title, meta description, first image alt text are the only items that have been shown to correlate with higher rankings). Another metric, Latent Dirichlet Allocation relevancy, has been shown to correlate as well - but it is essentially just saying "write relevant content".
2. Off-Site SEO: Yes, this matters the most. But right now you need to be risk-averse in terms of the anchor text that you acquire. The bulk of your links need to either use the URL or your brand name as the anchor text. For example, if your domain name is "freeforexsoftware.com", your anchor text needs to be either "freeforexsoftware.com" or "Free Forex Software" most of the time. Use brand anchor text and URL anchor text like this to build up your site authority, then leverage that with a smaller percentage (less than 15% per term) going to specific terms for which you would like to rank, like Forex Software or Forex.