Such an instructive post! I've learned a lot from the different POV's. As soon as the OP is asking for the collective's 2 cents I'm tempted to pitch mine in.
I believe there's a bit of an unfocused goal set operating here. If I had access to merchandise which I can sell at significantly lower prices than what is posted in Amazon, I would concentrate on making a killing INSIDE Amazon as an associate seller, definitively not on my own lousy start-up. What's your goal? You want to make money or you want bragging rights in the Big Box omni-merchant plaza?
E-commerce is a MARKETING tool, not a business end on itself. Nowadays you can sorta digitally "create" markets on your own. Once in a leap year. I've seen this a lot. People get enchanted by the e-commerce mirage, loosing sight of the fact that a lot of the big, successful names began at a time when all you had to do to succeed was to put something nice online. Market research and funneling budgets are not as evident as "the other" sellers success stories about making money selling the same stuff you sell at higher prices.
Wakabayashi and some others gave you sound advice in that your store is virtually indistinguishable from other big name ones, without the dynamic, browsing history content adaptation gadgetry. I fully concur: the only way you can distinguish yourself is through content enhancing. That process alone would clarify your store's vision and cull your catalog of dead weight as you will tend to ladle more content weight on those products that personally interest you more.
In my opinion you don't need to spend on advertising but make some marketing introspection first. You are wasting your money and effort if you just advertise without a marketing plan. Answer the big questions first: Who's your target? Where do they get their information and research for their shopping? How can you lure them to your shop? You can't just rely on good prices as shopping experience is way more important in your particular line of business. Online consumers are gluttons for value, and, as mentioned before, highly paranoid on their security. Market presence-wise you seem to be suffering from the ostrich's head in the sand syndrome. It seems to me that you have to make more efforts to appear in other SERP's than the ones you're looking at right now. Please forgive the stark similitude but imagine yourself standing in the sidewalk in front of Selfridges, with a rickety table strutting your stuff. How can you get people to pay attention to you and what you're selling? I believe you can, but you have to become a street wise shark.
Generally speaking, aversion to swift target (and means) change is not the right attitude to have in this business.