Regarding removing the file types:
You can configure different profiles for servers/media players. Most likely since you are already streaming, there is a generic DLNA device profile there. You can either alter that one or configure a new one.
Using the tree, navigate to Services and Plugins. Then the green DLNA logo with Media Network. When the Media Network page opens, go to configure at the top.
From there you can create a profile or alter the generic.
There is a pull down window for file types to convert. I unchecked them all.
I've just fiddled with these settings, then try playback and see what sticks.
Also, I have found if you are streaming to multiple Zones and the Music Cast app with Media Center, it's best not to link the Zones in MC as it doesn't seem to sync with the Music Cast link.
Regarding the AIFF files. Mine don't play either, but I've had previous issues with an external drive. My recovered files have many corruptions particularly to AIFF files.
I purchased YATE for retagging and reorganizing my library. The developers offer a free app Audio File Health Check.
You can find it here:
https://2manyrobots.com/plaster/In the end, I've found it easier just to convert most all of my files to FLAC, then they play just fine.
Often, I have experienced, files converted with MC don't always playback on different devices. (ie my car plays it but the portable device doesn't etc) I downloaded a free app from the Apple App Store : Sound Converter. The app itself is a bit slow and will crash if you give it too many to convert at once, but I've not had a playback issue on any of my sources. And you can convert to different sample and bitrates which I have found can slightly improve the quality.
Hope that helps