In addition to the advice above, I believe that isolating your particular issue is key.
Rather than 3 octave scales, you could play only the top octave of the scale, all on its own. You'll quickly find it fatiguing and annoying, probably. The next step is to break down the factors that make it difficult.
On the one hand, you have the left hand pressing down strings that are much higher than they are at the nut, and a vast black expanse that isn't familiar to your fingers. The easy part is to experiment with bringing your weight to bear on those notes, which will bring into question the angle of your hand, whether you collapse your knuckle joints, what intervals you will have between each finger.
Once you have found a comfortable and easy way to press down single notes, you then need to develop muscle memory for that particular region of the bass, absolutely separate from the rest of the fingerboard. Get really intimate with playing there, learn different scale patterns that only involve your thumb up there, try scales up the A and E strings as well.
The next problem is how to use the bow in this register. IF you come off the string, you will have to play a much more sustained stroke than in the lowest depths of the bass range. The strings ring at a higher frequency and don't sustain as long by themselves, which means you will need to use more bow speed. The tension is higher, so less weight is also necessary. As you travel past the first octave G, you will have cut the string length in half. Because of this, the bow needs to move closer to the bridge as you climb higher to compensate for the reduced string length and keep as much string vibrating as possible.
In playing quickly, you would do well to use less bow than playing legato. The string responds quickly in the upper registers and does not need as much momentum to set in motion. Less bow, moving towards the middle and upper half of the bow, will sound better than too much speed near the frog.
