Next check your gap. On the 3-roller mills, the gap needs to be set such that the area between all the rollers is MAXimized. If you think about it, you can set the same gap with the knobs in two different positions. Think of two circles that intersect, there are two points where they cross. Put the bottom adjustable roller in the lowest most position, 6, o'clock, on both ends. Looking at the mill from the drive shaft end, the drive shaft should be on the left side of the mill. You need to turn the knob on that end from the 6 o'clock position clockwise to set the gap you want. From the other end, you should turn it CCW. This will make the bottom roller as far away from the top idler as possible. You need to make sure that you set the gap this way so that the mill feed properly. If the ends are not set the same, the idler will bind. ALSO, don't set the gap wider than 0.045". You're wasting your time at a gap wider than that, and the mill might not feed properly, if it's bigger than that. I recommend you start at 0.040", and leave it there, or work slightly smaller.
Before you re-install the hopper, make a small mark with a permanent sharpie on the knob, and on the frames that line up, so that you know where 0.040" is on your mill. All milling is going to happen very close to here. This way, you can remove, and re-install the thumbscrews, and know that the knobs haven't moved, and you can always go back to 0.040"