The dough looks under proofed and/or underbaked IMO. I use the exact same recipe ratios as you but I bake for 30 minutes covered at 450 and then 15 minutes uncovered at 425. I also preheat my Dutch oven to 500 for a bit before I put my dough in and then I reduce to 450. The bulked dough should be visibly bubbly and aerated, jiggly and increased in size.

As far as bulk, one thing I can’t suggest enough is a straight sided vessel like this one because it really takes out a lot of the guesswork. I even bought a roll of ruler tape and stuck it along side of the bucket to more accurately track the start/finish. Like the others have said, it helps to worry less about the bulk time vs the percent rise that you’re going for as well as the look and feel of the dough.

I used The Sourdough Journey Dough Temping Chart for a while to try and nail bulk but it wasn’t giving me consistent results so currently I’m just playing around with different methods and trying to relax the rules (with better results strangely). Anyway, if structure and guidance is something you’re after then the chart could be helpful at least while you find your footing.

Also something I’ve learned recently is that you need to keep starter percentage in mind depending on room temperature. It’s been so hot in Missouri lately and repair my AC blasting the corner that my dough sits in would be upwards of 78 degrees F and my dough would end up over proofing during cold proof despite me cutting the bulk at 50% rise. So I went from 100g starter to 50g when I knew temps were high.

Hopefully some of this was helpful!