Sewing Tip #1: Okay, getting close.. (Tip to solving sewing machine tension problem..)

...but not perfect. I managed to fiddle with the upper thread tension to get okay stitches... Not perfectly even, but still acceptable.

Redid the leg hem.. The stitches look much better on both sides now.

I've also unpicked the stitches on the belt band.. Going to re-cut and re-sew it..

Belt band removed.

As to how I eventually managed to kinda solve the ridiculously tight tension problem.. VERY IMPORTANTLY, LIFT the presser foot UP BEFORE threading. This actually disengages the tension discs for the upper thread, allowing you to slide the thread in between the 2 discs properly.

Next, we need to adjust the tension for the upper thread. Remember, the smaller the number, the lower the tension. All the while I had my tension within 3 - 5 range, and I had no problems with it (it's also the recommended setting from the Brother's support page) but apparently, this tension is too tight for the thread I'd chosen for the culottes project. After some trial and error on a test fabric piece, the best tension setting that I finally settled on was 1.

Well, at least this kinda solved my problem. I believe it works the same on other machines and thread selection. Good luck!