In my view, off-handed comments are passive-aggressive and unfair, and if your T wants to talk about boundaries, he should just talk about them. I think you should talk to him as it sounds like either he's being really harsh or something has got lost in cognitive translation.

There have been things my T has said very carefully at first. He told me I lacked memories, and didn't know how I felt about things, because I wasn't used to giving myself that space. If he had mentioned dissociation, I would probably have freaked. I ended up gradually uncovering it myself. Ditto the fact that my mother is hugely emotionally neglectful. That must have been obvious to him from the off, but he couldn't just announce it to me.

I think you should talk to your T about how you are feeling. He needs to be straight about boundaries, and give you advice about how to manage the breaks.

As to boundaries, I do think it's important to recognise that your T isn't a spouse, or a friend. They can be there for you, but they're not meant to be at your disposal 24/7. If you're picking up on this stuff from your T, maybe stop and ask yourself if you are emailing too much and if the reason you think he's telling you that is because it's true. I find it helps to save drafts of things I want to send, and wait a few days to see if I still want to send them, and then I potentially just cut them down into one shorter email.