I've read the whole thread , I've looked at your product.

It looks good , the materials seem fine , but have nobody heard about ISOFix? At least in europe is standard in new cars.

The last baby seat that I used , manufactured by MassiCossi , had a better base than yours, with an adjustable aluminium leg and ISOFix links that kept it sturdly attached to the seat frame.

It was not cheap too, around 500 euro I think.

It was also removable with the press of a button , from the base and from the trolley

Edit: I missed a comment referencing it, then it seems strange to me that a seat sold as somewhat of a luxury item doesn'support that