Hello,
I am sure that I can help you with your PrestaShop multistore website themecustomizations.
I'm waiting from you a more detailed document to understand better the complexion of this project and to establish together the steps of it.
I am a PrestaShop Oficial Partner, with a 5 years experience in e-commerce.
If you are interested to discuss further more and fix all the problems do not hesitate to contact me.
Best regard,
Marius.