I would just slide it from the pot once it's well rooted in there, (another week or two, maybe) shift it to standing up straight, keeping the soil and root ball together with your hands as best you can, and put it back in the pot, putting potting soil around it to keep it standing up. You might even be able to do this without removing it from the pot. Just slide your hands down the insides and rotate it upright.
Don't worry. These are very lusty, resilient plants once they get going. You don't need to fret about breaking a few roots doing this. It will look funny for a few days, then correct its posture and start growing evenly. I would keep it in the shade and well watered until you see it start to grow again.
It will certainly break branches if the pot keeps falling over! Still not the end of the world because you can always root whatever breaks off.
It's going to be a nice little tree-like shrub by the end of the summer, probably 5ft. tall. You can't afford to let it grow like it is. Both you and it will be unhappy.
