Regarding the offline transformer voltage to use. When I have the actual transformer, I measure the actual secondary open circuit voltage. With the transformer already in the circuit, which I think is so in your case, I would just pull out the 5Y3 rectifier so you can measure the unloaded voltage. You can also measure the actual secondary resistance with the circuit powered down. I realize that you are already on the path to fix an issue with PSUD2 but it's nice to know the actual characteristics of your power transformer when possible. When I do the measurements that I described, I often find variations from the printed schematic values.
Cheers,
Tom
