increasing torque of a sewing machine motor
This is a tricky question.

On the one hand, it's clear that the larger motor will give you better torque. The combination of higher current and lower rpm should give about twice the torque.

On the other hand, there is no guarantee that this will be enough. To begin with, a motor will only bog down if the load is too great, and for a saw the load will be pretty much proportional to the feed rate. A basic question arises - if your saw is bogging down, why don't you just reduce your feed pressure and cut more slowly? Assuming that you realize that you could just cut more slowly, but don't, then there must be something else at play, such as the cut quality with slower feed and harder wood. So it's possible that using a beefier, slower motor will not give you an acceptable cut. And I don't know of a way to tell in advance.