Use this guide; "virginize" your wii again, completely this time. You shouldn't need to restore your nand backup because it doesn't sound like a brick, more like incompatible files from your updating, which could also be the reason your wiimotes keep disconnecting. Make sure you follow the guide, reinstall hbc/dvdx, after you get everything installed properly make a new nand backup, then post back if you still need help. But this guide was really helpful when I used it, so GL!
Next time your hdd gets disconn while the system is in USBloader GX, go in GX's settings and double check that your games are set to lad from WBFS, I have done this several times just to mess around, and when I remove my hdd while scanning through GX, the settings seem to change to a load the games from elsewhere, simply changing the game load back to wbfs(which should also list your hdd) everything returned to normal.