I think you logicked too far. In general, when the fed lowers rates businesses can borrow more and thus hire more. Yes this also makes us susceptible to inflation because more borrowing increases the money supply. The Fed uses two key metrics to decide interest rates: inflation and unemployment.
Okay so now let's introduce tariffs. Tariffs raise prices which to the Fed looks like inflation, so the Fed may respond by raising interest rates to shrink the money supply. As a result businesses don't hire as much and unemployment is higher. When unemployment gets too high, the Fed may lower interest rates again. I guess you're saying that at this moment labor is cheap and borrowing is cheap. Well that's if they drop interest rates really fast. More likely they gradually ease it back down.
Tariffs aren't some hack to bring labor prices down though. You extrapolated far into the future and then arbitrarily chose when to stop.