Cheekyfrog, I'm sorry to hear you don't really like the Ergo. I have to say I NEVER had a problem with the strap. But the position is crucial. Try sliding it up so it is almost shoulder height. I find it easy to grab that way.
With the fabric not being high einough, I really can't help. I can't quite picture what you mean either as my tall 2 year old still uses it comfortably and I can't say that the fabric doesn't come up high einough on her.
Having said that, the fabric is not meant to support the head. Is that what you were referring to?
Have a bit of a fiddle with the length of the straps and the position of the shoulder strap. You might find a position that suits you better.

I hardly ever wore DD on my back as I like to be able to see her. But once you get the knack it will be easy.

Sasa