Betsy, you can straighten out the main stem/trunk easily, but it looks like the branches are going all over the place. To straighten out the main stem, simply pound all the way around the pot with the heal of your hand to loosen the root-ball. Grasp the lower, thicker part of the main stem and lift the plant out. Loosen the soil so that some of it falls away. You want to be able to re-insert that root-ball so that the main stem is straight. Add soil, packing down firmly as you add it. You might have to place one or two sturdy stakes into that soil/root-ball and tie the stem to the stakes to keep it upright. All those branches/tips, being mostly on one side, will tend to pull the plant toward that side.
I would need more pictures to see just how many branches there are and their lengths. You might take several cuttings of one major branch with tips.
By the way, in my experience, I won't even attempt to root a cutting later than the end of September unless I know I can start that cutting in one of my greenhouses, and the later it gets in the fall, the less likely that will be possible. All my other tropical plants begin to move inside beginning mid to late October, and room becomes limited quickly. Plumeria take up a lot of room. Thus for me, rooting time is coming to a close.