Bodyfat impedance testing can be as much as 15% off, pending hydration and electrolyte balance. Not saying this to discourage you, just letting you know that if you decide to not drink water for the next 2 days - your scale will say you reached 12% no problem… even if you didn’t lose any bodyfat.
THAT being said, mirror definition always works as an objective marker - so long as you can objectively see yourself the way you are.
You said you can see a 4-pack, this is great progress.
For reference, ~8% BF looks like this:
You’re making great progress, just don’t focus on the number unless you have a real reason to do so (like stage competition).
For pec development - I recommend to just keep adding muscle everywhere. If/when you get to a point that you feel you need to specialize (bring up lagging bodyparts/make good bodyparts great), then you can do that too… But we are simply built the way we are in the end.
Good luck, I hope you stick around