What is your full connection string?
Since the fields in the DB Agent setup are essentially just building the connection string...
.... try editing the fields so that in the end, the connection string is as you need it.
I am not 100% sure this will work, but it's worth giving it a quick try.
Actually, the proper way of manipulating the connection string is in the Debug mode in client. When you're in the Debug mode, the "JDBC connection string" is editable.
You can enter the Debug mode by pressing Ctrl+Shift+F9 in the AppMon Client.