Out of the many that I have "sent to the dump" I have only one that did not stand up straight. It was on a fairly steep slope but I have caught many a good fish off it so I don't worry to much about them standing straight up. Here is a pic of it laying on it's side.
To answer your second question, I was once "disposing a set of three at the landfill" one early morning when a bunch of bass fishermen descended on me mid way through the deployment. Pretty sure the guy had seen what I was doing but later on ran a crankbait through them and got hung up. His partner cursed him knowing that I had just set them there and went in to get him un-hooked. I checked it once they left and it was in close to the same spot so I don't think they can move it very far before a hook straightens out.
My thought of a skinnier (but wider) base is I would be more worried about the concrete breaking up and the pile falling apart. I also like all the concrete being contained in the plastic bucket because I have a fiberglass boat and exposed concrete seems to like to rub all over it to prove a point. Just my 2 cents anyway.