Adding an external supply would work. however, there may be sequencing rules on which of the several power-supplies must be applied first.
Replacing or modifying R78 is a much better way. If R78 were parallelled with another, its value would go down and the voltage at VFB1 would go up: what you want.
I urge you to find somebody with a soldering iron and steady hands to parallel R78 with (I think) a 70.6K resistor
(You should also find someone who can commit to that number)