Are you truing the wheel on a stand, or on the bike?
One of the most annoying things to deal with is a bad hop.
Unless you have at least moderate 3-Dimension truing capabilities, your method of loosening then re-tensioning the spokes will inevitably give you a hop.
Breaking spokes is a problem. And it is not only weight&number of spokes. As others have mentioned, fatigue life, and perhaps the brand of spokes. I've been having some issues with an older 36h front wheel of unknown age, with unbranded spokes (3 broken spokes so far). Now I think that mixing DT and unbranded spokes may be a problem
as they may have different stretch qualities.
Anyway, as was mentioned, if you're doing 50% of the work to detension and retension 100% of the spokes, I'd encourage you to just buy all new spokes, and evaluate the rim at that time too.
How are you estimating spoke tension? The last time I tried to true by tension, my wheel was all over the place
I wouldn't worry about the exact DS/NDS tension. 2:1 may be close, but there are a number of other factors including exact wheel design, so you need to tension until you get the rim centred on the lock nuts. Just simply replacing the axle on my nephew's bike, and I threw off the dishing.
There are a few sub-$100 truing stands available. My father built my stand years ago (hopefully to be upgraded this summer). A pen is used to gauge wobble & hop (wobble is easiest to fix).
(teaching the next generation)