Why shouldn't he raise tariffs?
China has, within the past 72 hours, backpedalled on every single promise they've made at any point in these talks, reaching the point where they were offering nothing of consequence. Bull-headed and brash as he may be, Trump is teaching China "we are no tributary."
Frankly, I hope the tariffs keep increasing. The higher they go, the more manufacturers are moving out of China, which causes massive unemployment (at time when the Party can ill-afford social unrest and causes incomes to drop at a time when China's massive population of seniors depending on their children's financial support is expanding exponentially). China's economy is export-driven and they don't have the per capita income to switch to a consumer-based economy, so anything that deprives them of their ability to manufacture cheap junk is a devastating blow to their economy.
He knows how to hit China, and where to hit China, and if the US has to take a punch in the gut while they're breaking China's legs, so be it. In any fight, the winner gets hit too.