It's good to hear from you again.
Being frustrated & angry are easily understood. You are in a particularly stressful situation, which is 24 hrs a day, which ends in only one way, & you can't stop that happening. You are going to have so many emotional moments, sometimes brief & intense, when it will be nigh on impossible to not express in some way or other. You are feeling about what is happening, but because you can't prevent her suffering, her death, your loss, your son's loss, nothing, of-course you are frustrated & angrey . What is happening is painful, & it hurts like hell, in every way imaginable, but you don't have to imagine, like I do. You are living this experience.
& no matter what I say, you are there with her & your son, not me. How could you not feel at least helpless, alone & afraid, too? & you've said angry & frustrated. It's surely overwhelming your capacity to cope.
Do you think you could catch yourself beginning to express those emotions you would rather not take out on your wife & son? If so, could you all agree on a sign, a 'time out' sign, something like crossing your wrists in front of your neck, as a signal, you need 'time out', either a few minutes, or an hour,, whatever to calm yourself again? You could all use this, I think.
Can someone come in to look after your wife, while you & your son have some time away from being carers? Everyone needs a break from caring for someone. This is one 'self-care' thing, which is important to do.
I will continue to think of you, & your family,