strmchzr,
Wow, nice project!
I can't help but with a couple of your questions.
Unless you intend to redo the dam any trees larger than 4" to 6" in dia. should not be removed from the dam.
The willows need to be activly growing for best effect of chemical treatment. I believe Kelly Duffy once mentioned cutting slits in the bark & pouring a mix of diesel fuel & herbiside in? Hopefully someone will remember. Here's a thread on controlling willows:
http://www.pondboss.com/cgi-bin/ubbcgi/ultimatebb.cgi?ubb=get_topic;f=14;t=000015 To my knowledge there is nothing to keep beavers from eating your trees other than a tree guard around each one. Removing the beavers by trapping is best.
Someone else will chime in to help soon.
Sound like you're going to have a great place to duck hunt!
