You don't have to say those clients were yours, but you could say that you worked on "projects for" or some other creative verbiage around that.
> "The worst thing is to have people not buy, but have no idea what kept them from making the purchase"
That is very true.
My feedback: I visited your page and did not buy because I have zero revenue on my sites, and I have bought already so many things before (books, hosting, web templates, logo, etc) that I am in a "puzzled mood". I also did not feel the offer was for me. Right now my problem is figuring out how to make money out of my sites' visitors. To clarify I am one step behind where you are: I look at many options and wonder which way to go. Building a web app is one option, but it takes lots of time, and I would like to first get some confirmation that it is the right option to go for. Other option I consider is creating content (tutorials, forum).
I'm not someone super famous, but I have designed a lot of software applications used by companies ranging from Johnson & Johnson to Hobby Lobby. But they were clients of the company I used to work for (have since left), since I now work on my own I can't call them my clients.