Remod your system with Softmod any Wii guide to get it current. There's a reason we call that "brickmywii".
Don't delete, uninstall, or format anything. Just perform the mod as if you did it the first time. It will get everything current.
Since your purchased VC games are now failing, sounds like it messed around with your system IOSs. To fix that, when remodding your system, when you get to chapter 2 it will say that IOS Update is optional. Consider that a requirement. That should fix your IOSs.