More great work PLF!
I found two large trash sites on my farm after I started working in the remote heavy cover. Only later did I realize that both were places with significant erosion and the junk was acting as baffles to slow the flow of water. (I don't know how effectively the junk piles worked for erosion control?)
l think Bill's worry is about the high accumulation of organic material in a forest pond that could lead to an oxygen crash event - and would therefore harm almost any kind of mature fish population. (Hopefully, he will clarify since he is an actual expert.)
We have lots of tallgrass prairie on our farm. The leaves from our forested areas do not spread very far because our multi-level grass growth is very efficient at catching leaves.
It does look like you can establish good grass at your place if you clear the trees back far enough to let in the sun. Perhaps you could clear the trees a little farther back from your beautiful forest pond and plant a mix of grasses that includes some tall varieties or bunch grasses? That might enable you to have a forest pond WITHOUT leaf debris.
