Do you make this in a larger size or sell in bulk? We go thru 8oz in no time!

I don't know, but wish it came in a large sized refill. To save plastic waste and because I love this product. Hoping the manufacturer is reading your question and will see at least 2 customers feel the same about that.

My curls get frizzy between washes. Can I spray this on dry hair?

Yes, I believe it can help your frizz. I am an adult with wavy hair that tangles and frizzes. I use this conditioner daily on dry hair after spraying with water to moisten hair slightly. The ony negative is the scent. This spray in the pink label bottle is very sweet smelling--it is called tutti-frutti for good reason! I prefer the light scent of the SoCozy conditioner/detangler in blue label bottle. Both scents disapate very quickly, so it's not a show stopper.

Does this have Coconut derivatives in it? Coco glycosides, cetyl dectyl etc?

Not that I can see, but I’ve included a video of the ingredient panel for you to review for yourself.

Is the vegetable protein soy based?

If you have a child with a soy allergy and I would assume that it is soy. Your best bet is to contact the manufacturer. Vegetable anything typically means soy. This comes from a mom with a soy allergy kid.