A few questions for returned player

[Enkidoh]

1). I'm not 100% certain (as I haven't purchased any extra retainers myself), but it is my understanding that if you stop paying for that retainer then you lose all access to that retainer until you reinstate the subscription for it. I am very confident that anything stored on them is not lost and you just lose access to the retainer itself. Someone who actually has purchased an extra retainer would be able to properly clarify this though.
2). Unfortunately there is in fact no direct way you can transfer gil or items between multiple characters on the same account (you can only mail gil and items to people on your Friend List, and you cannot add your own characters to your Friend List because to add someone to your Friend List requires the message to be accepted immediately and is discarded if you log out) - presumably SE did it to try and stop gilsellers transferring their ill gotten gil around, but it's just inconvenienced innocent players. The only way you can really send gil between others is to use a third party you trust like a friend I'm sorry. :9