Hi Florian,
I don't know the ins and outs exactly of what you have but just thoughts in a very simplistic way as to how i might go about it.
Put everything in boxes and just ship back to someone you know.
List everything with values for customs with an explanation your heading home and shipping your collection in advance. List the correct customs tariff, for antiques used to be 9706.00.00.00, maybe it still is.
Whatever you get taxed, you get taxed.
Hope that helps.
Use UPS, as last time i looked they were the only ones shipping pointy things.,