... Don't ask me to work out which terminal on the transformer is which, that would require a few diagrams and lots of head scratching....
Funny, thanks! You have no idea how much head scratching and how many diagrams it took before I could put that simple PC board together - and I designed the #$%^ transformer just so we could do this dance!
For 4 or 8 ohms on the SEX amp, the windings are in parallel and there is no center tap. Balanced lines is short for balanced-impedance, meaning the impedance to ground of each side is the same. So you need an equal resistor from each side to ground.