Google Webmaster tools will tell your the click through rate from the SERPS and Google Analytics can be used to measure the conversion rate. You'll need to define your site goal and think about how visitors move through your site from their landing page to your site goal pages.

No, there's no ideal ratio as such and it's always a good idea to look beyond the headline numbers, especially the relevance of the pages being returned in the SERPS.

You're looking for good volumes of search traffic with as little competition as possible. While those large traffic numbers for highly competitive keywords may look attractive, you may be better off targeting less competitive keywords with smaller amounts of traffic.

Think of it this way a large slice of a small pie is going to be better than just crumbs from a large pie.

However there are other factors to consider beside just traffic and difficulty. You also need to think about user intent, relevance to content / brand / offering and once you start getting some traffic the conversion rate.

In a nutshell, it's the number of other sites that link to your page/site. You can find more info here:

https://moz.com/help/guides/moz-pro-overview/links/competitive-metrics

Number of linking root domains (# of linking root domains) includes only the number of unique root domains linking. Two links from the same website would only be counted as one linking root domain.

Engineers at SEOmoz have found that "# of linking root domains" is much more highly correlated to real rankings than "# of links".

Generally the more "connected" your page is to the the greater the authority the search engines will consider your site to have.  Not all links are equal though, and there are other factors involved...

Hope this helps.

How much difference has all these blog comments made? What other link-buidling activity are you involved in? Blog / Forum comments are pretty low-value.

How about picking a handful of the more authoritative blogs, with the higher numbers of subscribers and seeing if you can get some guest posting opportunities.

Blog comments are a great first step when building a relationship with blog/blog author, but you need to get involved in the discussion and not push your own site.

Once you've got some engagement going then you can approach the blog for guest post opportunities...

I think if you've commented on 1500 blogs then it's probably time to move on to some higher value tactics!

I really wouldn't worry about meta-keywords. Much better to spend the time on the content!