Hi there.
It certainly should be possible to turn a profit using woocommerce and Google product feed, we generally find that product feed ads work really well, and if you can make a profit on eBay, after fees, you can probably make a profit on your website.
SEO is definitely a viable option and the traffic is free once you get there, but realistically it will take time.
I wouldn't give up on advertising, but you need to work hard to optimize your feed to bring down the costs and increase the revenue.
As a starting point, make sure you have your products categorised correctly and install e-commerce analytics if you haven't already, then you can see which parts of your product feed are performing best. Increase spending on products that sell profitably and decrease your bids on products that are loss making.
Also, you need to work hard to increase the value of each new customer. In a niche with tight margins, you might have to accept that the first sale will not make enough profit to cover advertising fees, but if you can win a repeat customer, you will make that cost back many times over the life time of that customer.
I imagine that your niche is a great one for repeat custom, so focus on starting a newsletter and using promotions to bring customers back time and time again to your shop. Also, do the same with your eBay customers (within eBay's Ts&Cs of course) to encourage them across to your website.
Done correctly, your website business could easily be bigger than your eBay business.
That said, it is certainly worth working with an expert if you're unsure... But I would say that
