I also don't think you're expecting too much. He agreed to respond, and writing a few words in response to an email once a week really isn't that much work.

I totally understand how you feel. It drives me crazy when my therapist doesn't respond to my emails/texts, especially since I very rarely contact him between sessions. I don't expect long substantive responses--just something that acknowledges my existence so I don't feel like an idiot writing to someone who doesn't care enough to spend 30 seconds responding.