I'd much rather have only published 1 paper with a more expansive coverage of that topic. I feel intellectually dishonest because I know the end game is adding an extra line to the grant application/progress report.
From the outside, that actually sounds like very good work.
I also do research during weekends, but I've been experimenting with taking one day off to try to explore other things and spend time with my SO.
One of the reasons I want to leave is the work culture. I have the freedom to work whenever I want, but there are just too many deadlines to not stop working. Most of my labmates pretty much live in the office, although, they're all international students. I'm fairly disillusioned with academia now.
My advisor would be a bit upset if he knew I was taking classes. I know my research productivity has been down lately.
But here's the thing, finish your PHD. You'll be in the same situation in the "real world", when you have to work a job you don't really, really care about, and find time to explore other things you do. So start learning how to balance that now, while you've got the 'cranking papers out' down.
A few practical tips:
If you're wiped at the end of the day, get up an hour earlier and use that time instead.
Weekends.
Set very small, meaningful goals / questions / experiments you can hit. When you have to make time, it's all about momentum. If you get bogged down / unmotivated on your side projects, you don't stand a chance.
Good luck. Persevere.