OP, these are not step kids. These are step teenagers. The worst of the worst. They are at the age where they have mixed feelings about their biological parents, let alone their step-mom. They are at an age when parents have mixed feelings about their own biological offspring too!

American teenagers are usually pretty atrocious. They expect to be waited on like little kids but talk back like an adult.

Not sure what advice to give you, except that you are not alone. Maybe try to put some pressure on dad to get them in line and force them to be men and pull their own weight.