you did this guide from this site?
it covers everything you are asking for. like installing priiloader, blocking disc and online updates.
installing latest cios. you can stay at 4.3 when you do this guide but downgrading 4.1 is recommended as the other updates have nothing inlcuded to improve functonality.
your sdhc card problem isn't cios related, almost 100% sure, you tried to format them or buy another brand.. and at what ocasion they do not work? in a game loader in a mediaplayer?
edit: loading through disc channel only works with cios corp installed, not recommended, or with a modchip installed. i would keep the discs, get a nice usb harddrive, do the softmodding, and jump into usb loading. if you are lazy you can boot directly in a loader like wiiflow (check it out at youtube) browse your gamecollection (forget to say flip in your discs and save them to your harddrive using wiiflow).
do the guide again, read carefully