I completely agree that boundaries must be ones we can enforce and starting little helps. I learned too to only set boundaries for me, not with the expectation that it would change my addict. My boundaries were things to protect me from legal problems, hurt, stress, perhaps even physical harm. A nice bonus of some of my boundaries was that it did bring about some positive changes for my daughter, but I would have been in trouble if that was what I expected of my boundaries.
I think it is great that you can honestly say you are not ready for the consequence you believe should be the result of crossing your boundary. Recognizing things like that is a part of recovery too. Perhaps it would be helpful to start smaller. Hugs