But if I use a 1ohm resistor instead, I essentially am putting 5A through it, according to ohm's law.
I am not sure how you get that. If your rating is 0.5A @ 5V then if you put 5V across it you will draw 0.5A. Therefore according to Ohm's law the coil resistance is 10R. It doesn't mean you have to have a 10R resistor as well. If you do then you have a total resistance of 20R and therefore a current 0.25A only half the rated current. Mind you that is still a lot of current so I would be surprised if that gives you the small amount of torque you report.
What are you using as a driver?