Congrats on your new (to you) pond!
Your links are broken (to me), so I can't see any pictures.
There are so many topics in your post, that it may need to be broken up into separate posts so that we can take manageable bites.
I would start with taking the saplings off the dam. They could create a catastrophic problem. Also, it is only going to be more work the longer you wait, so do it first. Lastly, I tend to have better tree kill rates on cut saplings when the herbicide is applied at the proper time in the fall.
When you match the herbicide to your tree species, see if there are any recommendations on the best time to treat.
