It’s working so keep going with more layers.
A layer to remove protections, a layer to reinforce what’s already working, a layer to prevent him healing…
If you look at what Connor did in this link, it was a MASSIVE amount of work, he didn’t just throw the book at a guy, he threw several books at him. What you want takes a lot of energy and is counteracted by healing and time, so you have to keep pushing.
Also - hold off on the worry, as that will also cause it to fray and falter. Just persist.