I will try to answer all of your questions and also I like to ask you to wait until the new model is roled out in march to make a well informed descision.
If you are a shopowner you will be in control of the pricing. Also and this is not changing you are responsible for all the traffic to your shop. This means you need to advertise your shop to sell. This will not change with the new model.
What is it exactly what you mean with:
Only for the Markteplace we do SEO and SEA. This is also why we will have a different commission model from march on. We never did that for the shops.
As I can see all your sales are coming from the marketplace. But if you are interested in the best tips and tricks as a shop owner I like to invite you to go to the spreadshop blog. There you can find an amazing Selling Guide.
The external Marketplaces should not be of any concern for you. It is not like every design is automatically sold there via Spreadshirt on Amazon and Ebay. We are selecting specific design for those external marketplaces. If you already sold there via our external marketplaces you would see this in your statistics under sales channels.
I really hope you stay with us and give it all a second thought. If there are any remaining open question please do not hesitate in contacting us.