Dear V. K.,
If your 4-year old son would not be unsafe to leave him sitting at the table alone, I would find other things to do (like wash dishes, etc.) and allow him to eat at his own pace as often as your schedule will allow. Most fat people eat too fast. If we were all very slow eaters, most of us fat people would not have a weight problem.
I say let him eat at his own pace. He will likely be healthier than I am. You could possibly learn something by copying his eating habits.
Sorry you have to get up so early to allow him to have time to eat breakfast and go out the door at 8 a.m., but I don't see a problem with him being such a slow eater.
Now that I am older I wish that I had allowed myself to enjoy the simple things in life while they were happening and not wanted things to rush by as they literally did. I felt like all I did was change diapers when my two daughters were really young, and now they are over thirty and nearly thirty years old.
Enjoy your little one while he is little. He will be grown up and married before you realize it.
L. C.