Yes, it should solve the problem. But I wonder why the OT is down. The shop delivers quality OT, so there must be a reason why the OT is now as it is.
I'm just worried, that a new one gets shot again.
And no idea if the 6v6 are still ok, as I have no clue how they liked the test sessions at full blast with the steep reflected impedance.
Your 10W resistor was actually ok, as the delivered power was very low from the start. I was just worried that you used it at full blast before testing the amp with an instrument. Then you might have damaged the OT.
Also, as you checked your build several times, measured everything several times and that was ok, it seems that the OT may have been like this from the beginning. Surprising but possible, if they are not tested for function by the manufacturer (what I doubt for that one).
I would suggest you to get in touch with the shop using the standard manner (form in the website or email), explaining your issue, and the steps you went through.
Laurent