Hmm.... I don't think you can do this.
I'm not sure the OS on a MB bootable on a PPC. The way to try it out is to put the MB in target mode and hook it up to the Mini and boot the mini from it.
Secondly, SD will do the job, assuming the first issue works.
Thirdly, no, because when you put the mini into target mode, only the first partition will show up. (I think. When one puts a box with multiple logical disks in target mode, only the boot/parent drive shows up. I don't see this as being much different with a partition, but I've never tested it.)