Help going from two Apple IDs to one
As no-one has picked up on this yet, I'm gonna say "It's a toughie!"
I had my first .mac account in the 90's, a private email address for iTunes since 2001 [which I consider my primary account, as it's still my 'real' email address] & me.com [now also icloud.com] since the iPhone & the App Store started.
I have never found any way to successfully merge these identities.
me.com has all my 'cloud sync' stuff, iTunes has all my apps. I have them both set to the same password so I don't have to think too hard about it… & let it go at that.