Re: The "Talk" and other stuff
IMO, you're a bit late having the talk. Between myself and my closest friends we have 8 sons. Of course, we talk about them like mothers do. Mostly trying to figure out the mysteries of raising boys beyond feed them and hug them. They were all pretty much either full on masturbating or at least getting "morning wood" by between 9 and 10. How do we know? We thought they were too young for that kind of thing and walked in on them in the act while putting away laundry or going into boy territory to tell them to do homework or clean or whatever.
I'll never forget the day I sent my boy (then age 10) in to clean his room and didn't hear cleaning sounds after a while. So, I sent DH in to make sure the boy was actually cleaning up the Pit of Despair. All I heard was a door open and DH say "Why aren't you cleaning and why aren't you wearing pants!?!?" That was the day I stopped going into the boy child's room without knocking first.
I had the talk with my oldest two when they were 5 and 7, respectively. The boy was about 8 when I tried to have the talk with him, but his peers beat me to it, so I just had to clarify a few points.
Follow the evidence where it leads and question everything.