In Magento 1 you won't be able to get the price rules via API.
Also, as you saw, the catalog_product.list shows the list fo products without price. You'll need to make another request to get the product and see if the data you are looking is there (right now I don't remeber the full output with that condition).
Maybe, the final approach could be to create your own endpoint with the data you need: http://devdocs.magento.com/guides/m1x/api/soap/create_your_own_api.html
I also need Price Rule and Coupon Code API. I am not PHP developer but happen to work with it. Technically I want products which are on promotions. Please Help.