According to trade terms, strictly speaking, the factory is responsible for delivery. But I believe that your customer's freight forwarder has no authority to do customs declaration, verification and so on. So it's equivalent to saying that you have to do export declaration, collect US dollars, write them off yourself and refund the tax to your account.

The strict EXW quotation does not include tax refund, that is, if your customers declare their exports themselves.

I think what your customers want is to control the cargo rights to the maximum extent, not to find someone to write off the tax refund, so I suggest you do FCA, and your factory is the best site. In this way, the goods can be handed over to the carrier in your factory, and the customs declaration and verification are all your business, and the tax refund is also yours. You accept dollars.