Ron covered your options as they pertain to your first post. It will be necessary for you to periodically copy your .xml file over to the root level of the tree containing the music tracks for mt-daapd to use it as the basis for playlists.
Regarding your follow-up post, this type of set-up has been covered several times in the forum. Here is but one. It is not so much “fooling” iTunes into thinking its library resides on another server. Rather, mount the directory as a network volume (use “Map network drive…” from Tools and point iTunes to that share as the location of the library.