In the Late Ming Dynasty, from Veterinarian to Emperor?

Quantum universe, the bifurcation point of time and space, in the twenty-fifth year of Wanli, a man carrying salt died on the salt channel of Chishui River, with a hole two fingers wide in the back of his head. The county government approved six words: collect the corpse and bury it, and hunt down the culprit. The case was settled. His son was fourteen years old and had a few pockmarks on his face. People called him Li Mazi. His father told him a truth with his life: things in this world are unreasonable. He understood this truth that year, and for decades after that, he didn't expect anything else. He has no system, no superpowers, and no master falling from the sky. There are only two things he knows how to do: heal mules and settle accounts. He can calculate the price of food, foot prices, road consumption, and people's hearts; this is not a cheating story. This is a person's way of survival calculated minute by minute in the worst deck of cards in the late Ming Dynasty. But there was only one thing Li Gui couldn't figure out: how high he could climb without being easily crushed to death.