Ps3 – Is it possible to change from a PSN Sub Account to a Master Account

• To Log off your current user account, simply go to Account Management under Playstation Network press triangle and choose sign out. You can remove the saved password and it won't sign on to your user afterwards.

• You can log on to the same PSN account on different users, a user only separates media and saves but account data such as address and billing history is saved per account, therefore if you wish to remove your account from your daughter's user, you can do so without her losing the saves.

• If you wish to copy her saves to a different system user, you can do so by by using the Save Data Utility under Game, note however that some game saves are locked to a single PSN account and cannot be copied. In any case, trophy progress will be disabled when playing a save copied from another account

More info on account, sub accounts and users can be found here

You've over complicated this.

For PS3, basically once a DLC was installed on a system, any user on that system can play that DLC and earn trophies for it, whether signed in to PSN or not, I've never seen DLC which is only usable by the buying user except for items like Home items, Avatars and DLC for one specific game I know of.

So your "process" is fairly simple:

1. Log into the appropriate store for your game's region (you'll need another PS3 profile with a PSN account in that region)
2. Buy DLC from that store (funds could be from a local credit card or prepaid PSN card) and install it.
3. Log back into your main profile and account and play the DLC.

PSVita is different. A PSVita system and memory card is locked to a single user, so even if you switched the Vita's user (system restore), you'd still be only able to download the DLC to a memory card assigned to the "foreign user", meaning it won't be accessible to your "main user" (which will need its own memory card), this means that in order to buy DLC for a PSVita game, you must own a copy of the game from the same region as your main PSN user. There's no current way to avoid this (at least one that I know of), and it basically means any PSVita game that has "required DLC" like online passes, UPlay pass, etc, will only be "fully playable" if you buy games from your own region.