Biopellet reactors can take up to 6 months before you see any changes in your system. Remember that the biopellet reactor feeds the bacteria in your system, it does not add bacteria to the system. Your system has to build up the bacteria until it reaches a balance between the system, bacteria and the carbon that the biopellet reactor provides. Once that is reached, then you will start to see changes happening.
In terms of your feed pump, you should be pushing between 270-530 gph. If you are looking for a 3/4" threaded outflow, then I would go with the Water Blaster 3000 (http://www.coralvue.com/reef-octopus-water-blaster-3000-pump). Depending on the plumbing, you may be able to bring the water flow down to the 500s without using a ball valve.
You can also use the Water Blaster 2000 (http://www.coralvue.com/reef-octopus-water-blaster-2000-pump) which is right where you need it in terms of flow, but the output is only 1/2".