I believe the current config only allows tweaking the fuel value of some hard-coded fluid.
It will be great if one can add custom fluids for the boiler.

Also, can you add a config for fuel-to-steam and steam-to-power ratio?
This is to tweak the power generation to prevent exploits in modpack.

Not hard-coded, just add in the last line and DONE!

you can add new fluids to config