corys sell very fine long electrical screw drivers that will do the low flame bypass adjustment, i have 2, one i had to grind down the shaft just to do a single job, think it was a classique  from memory.
i would not recommend gameco manometers, i have had 4 of them and all failed within 2 years, not water proof, dont leave in the sun as the display disappears, basically rubbish.
try a sce digitron