I had exactly the same problem. Yesterday, I started to receive notifications that the phone storage was full, and I noticed that the phone was warmer than normal. Then, I saw that the the music app was trying to download everything from Match (around 17K songs) and there was no more space left, but the list of downloads was still there. In addition, my email box gets empty for some time until it downloads everything again and again. I tried to turn off Match, but I couldn't, so the battery was totally drained very quickly. I had to turn the phone off during the night, so it wouldn't drain the battery again.
This morning, I connected the phone to the computer and tried to sync it again. I turned iCloud off in the iOS, and it seems that it stopped downloading the songs, for now. But, my device still almost full and I can't delete "all songs" from it.
My opinion is that Apple is not good enough in the cloud. I didn't like the way the playlists disappeared from my phone after Apple Music, and now with iTunes Match everything got even worse.
There should be a better interface for iTunes Match where you can control its features and what happens to the devices linked to it.
I hope they can find a solution soon, otherwise this product will die.