Hi from Ireland. I just wanted to say I had the same problem with my brother until I started to use a thread bunny, or sometimes known as leaders and Enders - it just stops the fabric not being pulled through properly 😊

You are doing a great job. Keep making videos! If you start with a "leader" which is a small piece of scrap fabric, and sew that before feeding in your main fabric, it should help prevent the bird's nest of thread on the back of your fabric.

I believe where it says fold and has those arrows on it, it is telling you to place that end of your pattern piece on the fold of your fabric.

So cute! I am trying my first ever barrel pants. Very first project

If you pull the thread as u start to sew, it should  keep it from nesting

They turned out nice and they look good on you.
Ive made a lot of stuff from thrifted bed sheets. A couple of hints. First is look for the heavier 100% cotton sheets. They trend to work better.
As to the sheet you used, white tends to be more see through. Try ordering a Tie Dye kit and Tie Dyeing them a darker color set. Ive found it works well to make them less see through though you should only do it if the sheet is made from  cotton. ;)

They look great! Did you feel you needed to size down based on your measurements?