With your mod when you use Sacrificial dagger, you get healed instantly.

What is the expected behavior? I don't know Blood Magic well...

You expected to lose 0.5 heart per rightclick.
There is also charged rightclick, you lose all health exept of 0.5 heart.
And there is also a ritual draining you health 0.5 heart per second.

not sure i written all the interactions.

https://i.gyazo.com/5f7050756f03fa85fe1960eb8b51fdec.gif
Instead of hurting it healing.

Already on. I use scaling health mod

Try enabling experimentalSetHealth (Can be found under Main Menu -> Mods Button -> Click on First Aid in the list -> Config Button -> Show more -> experimentalSetHealth ). It might fix this issue.

Should be fixed by 8c5ee77