I have always trusted liquid pH indicator. I work in a lab and those cheap pH meters bother me irrationally, lol!
If your pH is above 7, the root (HAR HAR HAR) cause of the Mg issue lies below the soil surface... you're quite simply locked out.
Composted humus has a pH that is buffered at 6.8... hint hint! IF you don't have a reliable meter, go for reliable MEDIUM instead!
Yes, it's safe to transplant now.