Even edges are a challenge. I think that layout is the most important way to get even edges. You have to make sure that your layers of wool are the same throughout the piece especially at the edge. Also make sure to straighten the edges after first wetting down. I always rub back towards the center and along each side when beginning.
That said, it sounds like you have already finished felting and fulling. Would it be possible to cut a straight edge with your design? Could you show us a photo? You could cut and then rewet and heal the edges afterwards.
one thing to remember when trying to square up a piece is to not just pull the edges. You need to stretch all of it. If you along pull the edges the middle is smaller than the outside. We would love to see a picture. In the FAQ section, there are some ways to post. the picture has to be hosted somewhere on the internet like social media, a website or photo storage site. If you can't figure it out, contact Ruth or I and you can send it to one of us and we will post it for you.
Ruffling is caused by the way the fiber was laid out. It sounds like the edges have more fiber laid perpendicular to the edge and the inner fibers are more parallel to the edge. That causes ruffling since the fibers shrink in the direction they are laid. It is similar to the way you make a ruffled scarf.
Send me a photo by email and I will post it for you. laneruthe @ gmail.com
I might not be able to post until Thursday as I am not at home right now.
The pulling the middle helps with that too. If the middle is pulling in, it ruffles the edges. The other problem is often edges are thinner than the middle. When laying out you need to be careful that the edges don't thin out as they are wet and pressed down.