When my brother died, I felt like I could feel him everywhere. I had dreams about him and could imagine him perfectly - what it felt like to hug him, what his voice sounded like....
But then when my father passed, I felt very much like you describe. I felt totally cut off and numb. I still haven't dreamt about him yet. I don't know why some deaths affect us differently but they do.
I also understand your feelings about prayer. After my dad died, I didn't feel like praying at all. I used to feel something after going to church but I don't now. I still go and still try though - I am just hoping that it comes back someday. In the meantime, I just try to use that time to think about my family who passed away and recall good memories.