Now that you've got your wii in a stable state with nand backup, just run the ModMii Wizard, tell it your wii has never been modded before, then follow your custom guide. That will get all your softmods up to date and installed properly, including priiloader.
ModMii uses a modified version of the priiloader v0.7 installer that uses IOS236 (which should already be patched). The official priiloader v0.7 installer uses ahbprot and the IOS loaded by the HBC or w/e... so this tells me two things, 1) your homebrew channel is installed to use IOS61 instead of IOS58 (IOS58 is better as it offers USB2 support) and 2) the installer your using is missing the no_ios_reload tag from it's meta.xml (either that or the installer just doesn't like IOS61). Anyways, you don't need to concern yourself with any of this, just use ModMii and when you get to the install priiloader step it will simply just work, and ModMii will also make sure your HBC is installed to use IOS58 instead of IOS61