Not at all. Blaze powder is cheap as all-hell you know >.> Perhaps instead of redstone, Magmacream? :3
Magmacream is even cheaper. Also the Slimeball would "extinguish" the Pyrotheum. Bad Idea for such a Fuel.
Oh ok, only for less then 1500 K.
Much less OP >.>
Yes, that is not even enough for Aluminium, so you would have to use the Electric Blast Furnace for that.
Although you are wrong, all 4 components are super cheap. Unless playing with hardening mods, (as vanilla in comparison) I got to a nether fortress within 12 or so hours of playing.
Those one or two hours to find a Nether Fortress could also be spent in Bronze Age to get better Technology before going to the Nether, you know?