Altering Code for SEO

Hi,

I use the ‘HeatMap’ theme and recently installed an SEO plugin that doesn’t seem to work. I got GoDaddy.com to analyze my site from the SEO point of view and have quite a few errors (despite the plugin – All in One SEO). I then read somewhere it’s best to change the coding yourself. I request that someone guides me to do the following:

1-create/fix title tags for each page
2-create description tags for each page
3-create meta keyword tags for each page (I already have ‘tags’ but I wonder why meta tags are diff)
4-create heading tags for each page
5-The report says I have a lot of broken internal (14 pages) and external links (204 pages), but according to Google Webmaster, only two such errors exist. How do I discover these broken links?
6-prevent duplicate title tags on 14 pages.
7- what does this actually mean and how do I fix it: “504 pages have a highest meta tag keyword density of less than 2%”.

I’m placing a big order here and I’ll be grateful if someone helps me.

Thanks…