What will happen if my brother and I are executors and beneficiaries to our mother's estate but step-father is still alive?

My brother and I are executors and beneficiaries of my mother's life insurance and her will including her personal property and any property at the time of her death. Step-father has no idea she changed her will and everything went through her lawyer. He didn't have to be notified because their wills weren't mirrored. Does that make us, as her children and beneficiaries, entitled to her half of all property and assets at the time of her death? The reason I ask is because we have no relationship with him and never have. He despises us and I guess she knew he would change his will to exclude us after her passing or would take her half and give to his son. What does it mean since he is still alive? Will we need to request that all property and assets be sold or appraised and divided to account for what was the value at the time of her death? So that we get her half? I do know we will never have anything to do with him after this so I'm not worried about salvaging any type of relationship since there was not one to begin with. We just want to resolve this and not have something drag out. Also how do we handle her half of items in the home since he is still alive? We are not cold hearted people, but if I told you what he has done to her over their lifetime of marriage, you would understand the desire to resolve this and not look back. He will make all kinds of changes and sell stuff under our noses if allowed which is why we are so interested in resolving this timely. I just need to be prepared for what to expect and what our rights are. Yes there is a will and we are her POA as well. She is at the end of a very long battle of her disease and we have taken care of her at her request in her home because he doesn't.