Blackflame Covenant question

So recently I picked Blackflame Covenant node to convert my fire damage to chaos damage. So I want to ask this :

If I pick another node that says "Increase 12% Fire damage", do my skills now also scale with it ? Or do I have to pick nodes that increase chaos damage ?

Also was unsure on this and would love to know. Wondering is its worth using just for living bomb with ED/Contagion.