I agree with most of your advice but the PH must be adjusted somehow. Assuming there is enough lime in the soil is not advised since we know it is not buffering currently. Many people make lime amendments to the soil during transplantation for additional buffering. Although Lime is used generally to raise PH it is completely neutral. It will not raise the medium's PH above 7.0. He needs to raise the PH of his medium and there are few ways to do it. Adjust the incoming solution to the correct PH and/or add soil amendments to raise the PH.
Lets assume for a moment that the vinegar test is accurate and his meter is off by +1.1. Depending where he is adjusting his solution, he's most likely adjusting too acidic. The lingering question, what level is he adjusting his nutrient solutions to and what level is his soil runoff?
If you don't want to wing it on your ghetto meter you can get some paper testers. Assuming the vinegar test is working..... You could take a chance and flush with water that is adjusted to 7.5 on your meter which would hopefully be about 6.4ish actual and add amendments to raise PH. I would also re-establish nutrient base including CalMag.