Beware - this is a slippery slope - it starts with just one and before you know it you are enslaved to the joy of kilt making.

If the cloth will press and hold the crease then you don't have to stitch the crease - unless you want to. I now press in the pleats lightly along the crease so I can check the spacing and see how the cloth presses. Do it lightly and it can be undone and measured again until it comes out right. Doing the hem first is a good idea, by the way,

When you stitch the edge of the pleat down it makes a solid, shaped fell. You might want to find a stitch size and tension adjustment which will not mark the cloth and can be removed easily for the first trial. If you leave the ends of the seams not finished off - leave a long enough length of thread, just use a pin to pull the top thread to the inside of the kilt - then you can wear it for a while and see if you have made it too narrow or wide. If any of the seams pull open then you can make adjustments - you will have to do this before adding the waistband as you sew only three layers of material. Just baste along the waistline to hold everything together. If the sewing is correct then secure the ends of the threads either with a knot or a few stitches

The fell should fit fairly close, which is why I am a bit concerned about the back pocket. You know your own shape best, but you might like to consider using the top of the under apron forward facing pleat as a pocket. Even though they have the complication of the flare of the apron edge I have managed to put a pocket bag in hung from the waist with the pleat sewn down to enclose it. It seemed the natural place for a pocket. I can buy premade pockets here - though they are a bit flimsy looking. Handkerchief material might be a longer lasting option.

If my experience is any guide you will do enough sewing for three or four kilts to get the perfect finished article.