Agreed re the last.  I solved a lot of it by arranging the save matrices in a specific order on my chart, then when a save comes up that might fall into more than one area I start from the left and the first appropriate matrix I hit, that's the one gets used.  Thus, if someone gets hit by a magic effect that delivers a lethal poison is the save against magic, poison, or death*?  On my matrix death is on the furthest left, so it's what gets used in this case.
* - in 1e paralysis-poison-death were all the same save matrix; not all that long ago (during lockdown, I think) I broke them out into three separate matrices due to a bunch of what I think are good reasons, and so far I'm happy with the results.