iTunes has stopped updating my episodes

There is no evident reason for this. The feed validates and seems to be OK, and it can be subscribed to in the iTunes application and works OK there.

We've seen incidents before where the Store has apparently got stuck on individual podcasts for no apparent reason, though there's no way of knowing whether this is the case here. In these cases it usually clears itself up eventually, though it's been going on for rather a long time here.

You could try contacting Support at https://itunespodcasts.zendesk.com/hc/en-us/requests/new though I can't promise they'll be able to help.