I want to think that my words helped him in his rest, they made him go in peace, so much so, that his inert body reflected what his soul felt when he just died.

This is all that matters, you found your peace and so did he.

Saying goodbye to a loved one when they die is one of the saddest things that can exist, but I think it is very important to have that last conversation with them, one in which we make them feel safe and at peace, in which they feel at ease to leave.

I can confirm that as I've been in your shoes, unfortunately.