OP isn't selling things directly to end-users

That's ridiculous. If you provide a whitelabel solution, you simply add consent checkboxes and and explanatory text, the same way shop systems and virtually all other whitelabel software meant to be embedded works.

how culpable OP is for abuse of his tool's abilities

Regulators don't care where you sourced the software from that you provided. You provide it, you host it, you're culpable.