i found j.b's graver mods to work very nicely gettin into tight spots doing hobos. with great care, one can facet them the same as can be done on the normal size gravers.
i' d go with a 20. or even larger. you'll likely be asked to do a few things where a heavier vise would be better. the heavier one will not likely cause a problem on smaller items. jmho as for the "knockoffs", they generally aren't worth the money. a used victor will serve well. then too, you...
i think most any .5 will work. a difference of a mm or two should not matter. ugly but use hot melt to affix the lens in place. i did such for my leica. don't use super glue; it can fog the lens!!!!!
yes. many moons ago. i had a .25" square file, no heel, about an 80 degree face ! needless to say, everything i cut was a perfect disaster. in my defense, i didn't know what i was doing. then there was the "meeks book".
not sure if i ever cut that. one custom maker i worked for used repurposed blades from jrt engines. even in the annealed state were super miserable to cut
get yerself some windsor & newton china white. it comes in a tothpaste type tube. applied sparingly, it wont crack, flake, or rub off. the w/n version is the only brand i could conveniently rely on. dychem white has uses, but is a bit more tricky to deal with. jmho
my uneducated guess would be to first analyze the technique/s you're using to produce the ingot. are you using the same procedure from pour to pour? using the same procedure eliminates variables that can occur in the ingot. iv'e never done gold, but have experimented with silver, copper, and...