Since you have Four Swords, you can wait a bit. A new ARM11 kernel exploit was announced at 33c3 that would allow you to use
https://github.com/yellows8/3ds_dsiwarehax_installer/releases to inject the needed save for Four Swords to use dgTool and downgrade. Keep your eye on this page of the guide:
https://3ds.guide/dsiware-downgrade-(save-injection) (currently only for 11.0 and 11.1 as it uses an exploit that was patched on 11.2).
If you don't want to wait and don't mind transferring your NNID from the O3DS to the N3DS, you can do the system transfer method by buying a $2 DSiWare game off the eShop. See this page of the guide for more details on that method:
https://3ds.guide/dsiware-downgrade-(app-injection-and-second-3ds)