I’m sorry you are having such a hard time. I wouldn’t say that that cast on is rubbish, but as you have found, it is hard to knit from. I’m certainly not being sarcastic or trying to give you a hard time. If you are frustrated to the point that you want to give up that is always an option. Not everyone likes to knit.
I didn’t miss the part that said you are a novice knitter and I don’t think Jan did either. We have helped a lot of novice knitters here. It is hard for some people to learn just from videos or pictures or words. Maybe you will be able to find someone to help you in person if you can’t learn it this way and don’t want to give up on knitting entirely.
The reason we are suggesting you try another cast on, is because you have discovered on your own that knitting from the backward loop can be hard. And that is not because you are a bad person, it is because of the cast on you are trying to use.
What I was going to suggest is that with the skill you already have doing the backward loop cast on the way Amy shows it you could quite easily learn to do the long tail cast on. The way I learned to do the long tail cast on is listed in Amy’s videos as the “Alternative Method”, or “Thumb Method”. And I think it is a little easier to grasp than the “sling shot method” doing it all in one hand. I still do it this way and I teach it to beginners including young children (but in person; you still have that disadvantage).
If you look at Amy’s video on how to do the long tail alternative method, you can break it down into four steps and you already know the first one. She does it with her thumb, but it is exactly the same as what you are doing with the backward loop cast on with your index finger. You don’t have to use your thumb.
You have to start this cast on with a “long tail” (it seems like kind of a misnomer since it is the short end)of yarn off to your left and the yarn from the skein on the right. In other words don’t start right at the end of the yarn.
Watch the video and along with this you may be able to get it. Using the long tail part, start just like the backward loop up to the point where you have the needle through the loop on your finger. Then with the yarn that goes to the skein wrap the yarn under the needle, like she does on the video. Then take the loop on your left index finger and put it over the needle and pull slightly on the “long tail” (the part you used to make the loop on your left index finger).
Like I said, watch the video. What you do at the beginning of the backward loop will work for that first part. Then just wrap the yarn, put the loop over and snug up the stitch.
Learning new hand skills feels awkward for everyone at first. Don’t be too hard on yourself if you have trouble and don’t be too hard on us for having a hard time trying to help via computer. Someone else may have some advise on making the backward loop work for you. I can’t do that, but I offer this.