It may not be as much work as you think. First off, I would get rid of that stock style belt tensioner you have next to the blower pulley. That is most certainly part of your issue.
If you ever get the chance to watch it on the dyno, watch what happens with one of those tensioners every time it quickly come on and off power.....they ratchet back and forth momentarily reducing the amount of tension on the accessory pullys, causing them to skip. That alone could explain some of the dust. I also see that your makeshift apparatus to hold the tensioner in place looks like little more than some long bolts, sleeved inside of some hollow stock cut to the appropriate length. That's going to flex like crazy under load. Comparatively, the Vortech brackets are made from a single, solid thick piece of steel, much stronger than your set up and they flex like crazy with very little tension.
Improving your situation is certainly doable, without having to completely redesign your accessory system. First off, your blower should run independant of the rest of the accessories. Nothing more than a crank pulley a tensioner and the blower pulley. This will then allow you to look into an 8 or even 10-rib set up. You may even get away with a stock size blower pulley and that itty bitty thing you run then. Keeps it simple and more importantly if you ever throw a belt, you won't end up stranded on the side of the road because your water pump has stopped turning along with your blower.
Second, Eaton sells half a dozen different length nose drives for their blowers. You could easily bring the snout length forward, without having to disturb the rest of the system at all. This will then allow you to run a 2-pully crank set up....and more importantly a larger diameter outer pulley to spin the blower.
The tensioner should be redesigned anyway, so this would be your opportunity to move it outward and replace it with something solid like those sold through Vortech.
If that sounds like too much work, or money I would at the very least redesign the tensioner set up with something more sturdy and exchange the spring tensioner for a sold one. Then I would bump that pulley up to at least 2.5" (perhaps something of the anti slip variety as well) to get more consistent traction on it.
The torque comes on and peaks a lot earlier in the power band than the horsepower, greatly reducing the amount of slippage you're seeing in that area. The horsepower on the other hand peeks much higher in both engine and accessory RPM, which is where the most slippage occurs. Get that under control and I bet not only your power curve will be more uniform, but so will your fuel delivery.