[Crex]

I'd focus on getting the forge reconfigured for more optimum performance and worry about the steel last. It'd help more if you could show the forge in operation. From here it looks like you took a good design and made it less good with the addition of the firebricks. As suggested another layer of wool would have served much better.
Not being able to see how the torch enters the chamber, flame characteristics, or interior dimensions make it difficult to diagnose with any accuracy.
In 35 min of run time most of us would/could/should have several blades forged out and ready for profiling and HT. Sounds like too large a chamber with the bricks sucking up all your heat and maybe an inefficient torch. Whether it's blown or venture shouldn't matter much...other design problems are far bigger issues.

No specifics on what steel you are using, however it's very unlikely it is the steel. You comments about temps are somewhat vague. What are the actual temp ranges you think you are working with? How are you determining critical temp before the quench? What quenchant medium and temp?
Note - The oxidation color on the steel from drawing the temp is only indicative of surface temp. How are you controlling the heat? In what kind of oven? Is it possible that you laid the blade on an oven rack with spacing matching the spacing of your hard soft spots? If so you did not let the blade soak long enough at tempering heat to fully temper.
Awful lot of variables to sort through with just the steel issue.