How old is the Ergo? I would not repair a carrier, if it is showing signs of wear. I would replace it with a new one that comes with manufacturer warranty.
Cotton German style woven wraps are wonderful from birth to toddlerhood. Blends can be harder to break in and for some hard to find the comfortable "sweet spot". I say go with 100% cotton, learn how to pull your wrap to tighten it up to make is super supportive for your baby and you.
Have you Googled for a local babywearing group? I would recommend you try to make a meeting so you can touch and try a variety of carriers. Then make a more informed decision. For some smaller people an Ergo maybe to big. There are also DIY wrap idea and how to forums on Thebabywearer.com
Do you breastfeed? Does the baby show a preference to one breast over the other? Babies sometimes are out of alignment because of utero, birth position, birth trauma. These babies tend to show a breast side preference and sometimes hold their heads to one side more than the other. Sometimes baby will not be happy in a carrier because of this.
If it is not this I would try again maybe use a different position in the carrier. I would suggest you go back to the Moby...
I would order a woven wrap conversion from SBP here. http://shop.tadpoles.ca/-Woven-Wrap-Ring-Slings_c_3098.html
I think you will get your best size this way. Ergos are not really made for use without the infant insert for newborns.
Try the following places for wraps under $100.00
Thebabywearer.com the For Sell or Trade Forum
Ebay.com all of these places would be good places to look for a used wraps.
BBSlen maybe a good choice fro brand new under $100.00.
You can google for instructions on how to make a woven wrap from a tablecloth.