Bullseye, Unique, and 231 will all work quite well. For target shooting, why not back down to 200gr slugs in your .44 Mag cases?
One issue I've run into with longer barrel 44's is that you can't get the rear site low enough to shoot 240gr slugs point of aim-point of impact in the low velocity target loads. Going to 200gr solves this problem...and saves some money on bullets as they cost less.
On Friday I brought 600 rounds to the range. 300 .357 (really .38 target loads in .357 brass), and 300 .44 Mags (really .44 Special in .44 MAgnum brass)
The powders I ran were Bullseye, 231, and Unique. I used 5.5gr, 7.0gr, and 7.5gr respectively under Xtreme 200gr plated slugs. All worked very well. I was most pleased with the Bullseye loads. Very light recoil in a 4" 629-1...felt like a .38. At 10 yards the group of 100 rounds was slightly larger than a gold ball.
You're on the right track for target loads. I would suggest trying some different bullet weights. Xtreme has free shipping going on right now, which kinda makes them the best deal at this moment.