Thanks for spotting the error with the heater value. I corrected the layout posted above,
The 4558 is a dual opamp. The schematic lists 1/2 RC4558. That means only one op-amp of the dual package is used and as such the nonlisted pins where not used. My layout uses a TL071 as it's a single op-amp and the pinout is slightly different. Download and compare the two different datasheets and you will see the differences and similarities between the two.
757R means the trimmer was adjusted to 757Ω (ohms) resistance. The two symbols Ω and R are interchangeable and mean the same thing.
The +9V is the V+.