I am so very sorry about your little Gabriel.
I used to wake up in the morning with racing thoughts and I felt so overwhelmed with these intense feelings. My chest felt as though an elephant would stomp around on it and I had difficulty breathing. I could not wait to be able to go back to sleep again so this would stop.
Any relieve from this seemed better than to endure any more of it.
If you feel anything like I did, then I can quite well understand moments where you have thoughts you are describing. I also think that if we are faced with death by loosing a loved one, we start thinking about it differently and life does not seem so indestructible, but a lot more fragile. We start seeing many moments where death could occur, we are more aware of it.
There will be the day where you will feel a bit better and will be able to string together some good moments, and eventually days. Be gentle with yourself and don't be afraid to ask for help if you feel you can't do it on your own.
Will be thinking of you, your family and your little Gabriel.
Sending you hugs!