I'm so glad this didn't end up being a painful, and or, an expensive lesson to learn. In reading numerous posts regarding squibs, I often get the impression that some simply don't view squibs as a serious problem. In fact, a squib has the potential to be just as serious as a double or triple charge.
Personally, I've never experienced a squib, and I've been reloading for 30+ years. But if I was experiencing extreme velocity variations such as the OP did, I would have stopped shooting those, take them home and pull the bullets, and then proceed with verifying the charges on a scale.
I would then devise a way to introduce multiple fail safe loading habits into process to prevent any mistakes.
There is obviously no problem with using powder measures, as long as you verify the charge on a scale every 10 or so rounds. If the measure is producing good reliable load weights, I'm sure, instead of every 10 or so rounds, increasing the number between scale verification's can be expanded. But that's something the OP will have to decide, based on the verification results.
Powders can do some weird things in the hopper, like jam or funnel, which results in inconsistent charges, and sometimes those variances can get extreme. Static is another issue that can cause problems with how the powder flows from the hopper.
But even when weighing every charge on a scale, still, things can happen that will result in the wrong charge being loaded. I've had registers, ceiling fans, lighting fixtures, static, and various electronic devices, all of these can factor in, resulting in unusual and sporadic weights as well.
So the best advice I can offer is to verify, verify, and then verify again what weight charge is being loaded. And I certainly understand the desire for some to find the most comfortable load to shoot, but be cautious as to how far down you reduce a load in addition to positively verifying the resulting charge.
And again, I'm glad this didn't result in you getting injured, or worse.
GS