Maybe push the pickup in a bit to take the pressure off the screws when you are unscrewing , I’m guessing there’s foam or a spring underneath pushing it up 🙂
The D and G strings do sound a lot quieter with the thumb, so I tend to add a bit more pressure to compensate or turn the volume up a touch, I also find some Basslines sound better, especially some of Flabba holts ones, he plays with the thumb a lot
I’ve got a few days off and was playing around with different tones on my recent amp, and I ended up starting to learn this, I found it a bit trickier than it first sounds, it’s a great Bassline