Hi Susan,
Sorry to hear about your problems, it's something we've experienced too as an ecommerce company working with several sites. Although we haven't been hit as badly as you, we have experienced a drop in traffic but luckily some of our sites are recovering now.
In answer to your question, I think Google has made a bit of a mistake by promoting Amazon and eBay listings and we're still hoping that they're working on a fix. However, I'm slightly concerned that you've spent so much money, including your savings, on trying to get your site back on the first page without any results. I'd be interested to hear what you've done because, for that amount of money, you should have at least experienced some gains.
I would say the number one factor working against you is your exact match domain. You may have had it for years but having that as your domain probably hasn't helped, especially with Google punishing EMDs recently. Maybe it's time to consider a change?
Secondly, I'd really work on your meta titles, meta descriptions and on-site content. Remember it's not all about keywords, so make them user friendly and really appealing to people in SERPs. I've also seen the meta keywords tag that is stuffed with keywords on your home page - I'd clear that out too.
Third, what's your backlink profile link? It might be time to have a thorough clear up, fishing out any bad links and disavowing the ones you think are hurting you. Any good, honest SEO company should be able to do this for you. Once you've done this, focus on getting really good, natural links to your site through social sharing, writing content etc.
With the amount of money you've spent, I'm concerned which companies have been working for you and whether they've followed best practice. Anything you find here on Moz is really useful and I'd recommend doing as much as you can yourself so you know it's right. And make sure you know exactly what your SEO company are doing so that it doesn't harm you in future.
Hope this helps!