[GT289]

Wow, all sorts of replies, and about 90% of them are ignoring the fact that the OP has combustion gases entering into the coolant. I would get another set of head gaskets and give it another go. Perhaps add a bunch of fans to keep the engine cool while breaking in, but focus in on fixing the head gasket leak before fixing anything else.

Yup.
If you get combustion gasses in the coolant, however that’s happening, that needs to be the first thing that’s addressed.
The cam may already be toast. If you can’t get a full break-in done because something interrupted that process, you can shut down the engine, let stuff cool down (obviously fix any issues) and refire the engine to complete cam break-in.
The way the OP’s cam break-in is going, that may be “out the window” at this point.