At first thought, it came to mind that you must be doing something incorrectly if you are breaking needles. I don't recall ever breaking one, but I have only hand stitched the equivalent of maybe 200-300 hours. If the awl-pierced hole (drilled, punched, etc) is of sufficient size then theoretically you should never break a needle.
I been trotting along happily with size 1 needles. I'd go smaller diameter if stitching inlays or thinner materials.
Added: By the way, Campbell-Randall is a great supplier in my experience. I use linen thread rather than synthetics and the Barbours pure flax sinew 5 cord natural color left-hand twist is what I use in almost all cases. I purchased a 1,094 yard spool and still have a long time until it is depleted. I like this thread because it can be dyed and stained the same color of the leather, unlike some synthetics.