Help monetizing a Clickbank affiliate authority site

I recently began working on an authority site, how-to-get-abs-expert (add a .com to the end). I'm gradually building it up, and so far its pages have been doing quite well in the SERPS rankings. Overall, the site is beginning to get a really decent amount of traffic. I currently have nine different pages ranking in Google's top 10 for the respective keywords I was trying to rank for. Most of these would be considered buyer keywords, and all of them get at least a few thousand exact-match searches a month. I planned the whole endeavor pretty carefully, and the rankings and traffic tell me that I'm doing something right (just to note, Google is my only traffic source right now). The problem is (and it's a huge one), my CTR is extremely low, and conversions are basically nonexistent at this point.

All of my pages are using the same basic setup as my home page. The articles I'm using are not really of high quality, so that's not going to help things much. If your experience has shown you that the quality of articles in this type of site has a major effect on CTR, I'd like to know about it..

At the moment, I'm attempting to get people to opt-in with the promise of a free eBook, which is a rebranded version of one of my affiliates' eBooks. Not much luck there so far in terms of actual percentage of people who opt in.

The products that I've attempted to promote have mid-to-high gravities. That fact alone leads me to believe that, although my hops haven't exactly been stellar, I should have gotten at least a sale or two at this point. I do recognize that people looking to get abs may not be the most 'desperate' buyers out there.. in fact I'm strongly considering the possibility that I've just picked a really, really crappy niche that by its nature does not convert well, though the fact that these products have good gravities would seem to be at odds with that..

What is considered to be a decent CTR for sites like these?

I feel like this monetization is the last piece of the puzzle in getting my sites into moneymaking territory, so any input, examples of similar sites that have been successfully monetized, etc. would be greatly appreciated. As of now, I'm a bit baffled at the lack of results.