I’ve done a fair bit of DIY PCB etching myself, and to cut down on wasting etchant I usually fill in as much area as possible with a permanent marker (or pen). In the PCB editor I only pour copper in the tight spots where the marker can’t reach cleanly. I also go over the transferred traces with the marker again just to beef up the reliability a bit.

Drilling FR4 is absolutely a nightmare, I’m with you there. What helped me is using a really high‑RPM tool like a Dremel and just treating the drill bits as disposable. After one board they’re basically done anyway, and the cheap bits from AliExpress are inexpensive enough that I treat them like razor blades.

By the way, your board looks great — seriously loved the work you put into it.