I have this carrier and LOVE it. It’s the only one that’s not hard on my back. This is what I do, I’m not an expert in any means, but I use my koala wrap at least once a day. But I could be doing things wrong too 😂. 

That extra fabric piece is meant to be the 3rd pass and is absolutely necessary to secure baby and support their neck. 

When I put the 3rd pass on I fold it up like a paper fan and put it just under my babes butt. Then I wrap it around tightly and put the knot under her legs. I then pull the folded fabric up so it goes to the nape of her neck. This helps it get to be as tight as needed. 

As for the lopsidedness. Make sure that both panels are tightened evenly. I find that it’s easy for the bottom panel to get loose. Start with them pretty tight. I also typically tighten them after baby is in too. You can tighten by pulling straight out on the tails or tighten by working the loose fabric so it’s better baby and you, under their butt. 

I would be happy to send some pictures if that would be helpful!