Hi there,

Is it correct that you are using the "Cream" order form theme? 

To remove the top bar with filters and search, you can add the following CSS to your site:

.b2bking_bulkorder_cream_header_container {
    display: none !important;
}

To remove the qty, please add:

.b2bking_bulkorder_form_container_content_header_qty_cream, .b2bking_cream_input_group {
    display: none !important;
}
.b2bking_bulkorder_form_container_content_header_subtotal_indigo, .b2bking_bulkorder_form_container_content_line_subtotal_cream {
    width: 27.5% !important;
}

To change the Add to cart text, you can add this PHP snippet:

add_filter('b2bking_cream_order_form_add_cart_text', function($txt){
	return 'Cart';
}, 10, 1);

Regarding the font size, this depends on each element, but in general you can add this CSS to change it for most:

.b2bking_bulkorder_form_cream_main_container_content div {
    font-size: 15px !important;
}

Kind regards,

Stefan