New to the whole dread-thing :-)
Oh boy. So many red flags here. I'm gonna let SE take care of it when he gets here but here are your main problems:
Watching youtube dread videos. Major mistake. A good amount of them use horrible methods. In addition you are tailoring your dreads after some one else's and basically diluting your own individuality in the end product. It's not really an experience, it's dread cloning.
Crochet. Using a crochet needle effectively just set back your dreads an additional 6 months of recovery. The hair grows extremely slow. Very Very bad for the scalp. Look up traction alopecia that's what crocheting causes. It makes your hair roots weaker than normal over time and they will eventually break off. In addition they create the look of "manufactured" dreads also that look identical and robotic.
Dread Extensions: Okay so I'm really not sure why you would use those as you said your hair is about 4 inches long. Depending on your hair texture (especially if you have African texture) your hair could've naturally started dreading by itself. If it's not that texture you should've waited for it to grow out more before deciding to TwistnRip.
I hope you take a look at this before things get kinda bad.