Mustang, there are two ways where you might be able to help them out. Medically, it is out of your hand as is often the case in these circumstances. You can only do what is within your ability for your step-Dad's physical comfort. There is, however, another thing which you can do for him which would preoccupy his thoughts and give him peace. You mentioned that he has gone back to Church. Perhaps, you can find him some reading materials with regards to that. There are many which are peacefully reflective, and healing. It might helps towards that element of fear. You can also ask if he would also want to speak to someone from Church.

As for your Mom, helping out with shopping and the house would help greatly. Both of you can perhaps find the comfort you seek under the circumstances. In this case, you can allow conduct to reflect what you want to say.

It is admirable that you continue to reach out to your Mom, Mustang. For that you are blessed and I shall carry all of you in prayer.