If the wishlist does not work to add the product to the cart, then it is a limitation of x-cart which would require extra programming and cannot be provided through instructions as testing to find the correct code would be required.
In order to edit the product pages and remove the add to cart button on those pages, you'd have to edit product.tpl
You'll have to work some of this out yourself or purchase some custom programming
You can use this in a mail tag:
<a href="mailto:Company Name <youremail@domain.com>?subject=EMAIL TITLE - {$product.product} - {$product.productid}">