I think it's good that you've identified the responsibility as yours, that shows how healthy you want your son to be.
My ex SIL's father was killed in a car accident, and she suffers from this same anxiety that you are describing.
What calmed her fears is that each week she wrote a letter to her kids and put it in their safe so that in case something happened and she was suddenly gone from their lives she could have said exactly what she wanted to her kids. She didn't leave the old ones in there.... just one letter to each of them. Maybe try that.
I also think you can try a simple cognitive behavior exercise. It's called "translation" and it's where you swap out meaning for certain things. Work with me here.... I'm going to make some assumptions.
In your post you make the statement "So what if I get hit by a bus on the way back to my office and my son's last memory of me is walking out without even looking him in the eye?" and "...... and look him right in the eye and tell him how much I love him.... ."
You're associating eye contact with love and assurance for you that your loved ones know that you love them by the fact that you make eye contact with each other. You indicated it twice in your post. This is a big thing for you.
So - what you have to do is *translate* the meaning and swap it out for something that is better for your son. Better for your son = better for you.
You want to "make eye contact" with your son so he knows you love him.
Instead of doing that.... pick something else and translate the meaning.
You want to "give him a high five before you leave the house" so he knows you love him.
You want to "kiss his forehead right when he wakes up in the morning" so he knows you love him.
Make it less important that it's about right when you leave him and MORE important that *whatever the behavior the two of you pick* is at least once a day, or right when he wakes up or right before he goes to sleep.
It's just a simple swap out of a word and a small behavior change that will hugely impact each of your comfort levels.
Good Luck.