Advice about online shop - selling Vitamins via Shopify & Amazon

I would like expert advice about how to increase my online business - by 10 times - in the next 3 months
I started the business in January 2016 and the current level of business is not satisfactory

I use Shopify for the online business at: www.greenvits.eu
70% of these sales go to UK and 30% into mainland Europe
Note the Currency Converter

The products are premium vitamins and supplements which are high quality, high strength, hypo-allergenic and in large pack sizes, so the prices appear high compared to a lower dose size in a supermarket.

If "Jane Public" visits my site she does not know why she and her family would benefit from stronger vitamins in large packs, so she has a quick look and goes away.

Some people stay longer to read the blogs and watch the videos.

One person suggested using Facebook adverts to attract visitors to Facebook videos which educate the potential customer before bringing them to the online shop.

I can attract visitors but the conversion rate is low
Natural organic traffic comes from the built-in SEO and a few high quality back-links
These have a conversion rate of about 3-5%
A recent Facebook advertising campaign created 90,000 views, 900 visitors - but only 1 order !

On www.amazon.co.uk I sell 2-3 times more than the online shop
You can see the products by searching on Amazon UK for "greenvits"
I don't know how to boost the business on Amazon

I sell a tiny amount on www.ebay.co.uk

Google Adwords is not currently cost effective
If it is relevant, I would like to see suggestions about how to improve this

I am not allowed to SELL Vitamins on Facebook
However, I would welcome suggestions about how to attract the right traffic via Facebook
Search on Facebook for: GreenVits

I have a low key outbound campaign via Twitter: @GreenVits1

I have not yet tried Google shopping
I have not tried other shopping portals like Etsy, etc

I have a Mailing List of 600 customers who have bought during the past 2 years
Many of them have placed repeat orders

I would like help to make a strategic review of the current business and how to increase it - significantly

I would prefer someone based in the UK where we can meet face-to-face occasionally
I live in NW London
Alternatively we could share screens via Skype etc to discuss the detail reports on Shopify & Amazon
.