In my answer to your other question, I mentioned
If the behavior persists or escalates, especially if it persists in specific people, other steps or considerations may be necessary.
Most of your bullet points describe immature thinking from an immature person exercising his imagination and testing his limits. I have seen this before, almost exactly as you describe, from players of similar ages when I was in school. It's testing boundaries, and is often self-correcting. In one case, our group simply stopped inviting one person to games after school.
Your final bullet point discusses a line that must never, never be crossed, no matter the age of the participants. Your last bullet point describes attempted sexual assault.
Unwanted contact is assault. Unwanted contact of a sexual nature is sexual assault. This passes beyond the level of immature and undesirable, into criminal behavior.
I have dealt with this as well, though not as a teen.
The first priority here is to take steps to eliminate the threat of assault or sexual assault. I realize this may not be possible for you alone. If possible, have an adult intercede. If you're playing in school, get a teacher. If you're at home, get a parent. If you're in public, find someone who works a the venue.
Other steps you might take include, schedule games when the other player can't attend, or cancel them entirely if you have to. Whatever you need to do to ensure the safety of you and your players. It's only when that happens you can reasonably consider what do do next.
Once that safety is assured...
You may, if you think it will help, have a word with the player. It's possible the behavior is only boundary testing and the player will stop once boundaries are clearly established. Not certain, but possible.
If you do talk to him, make the discussion about you and your feelings. Don't speak for others. Tell him how you feel, and make it clear he should stop. And if possible, make it clear this is a zero-tolerance issue, especially with regard to assault.
You may also talk to the other players, and specifically the victim of the attempted assault. Their input matters here, hers most of all. But, if you can find a level of assurance from the player which satisfies all the others, you can consider letting the player continue with the group.
One other note my daughter just added for me. It doesn't seem like you're considering this, but just to be certain: don't penalize the girl for the actions of the boy. Don't remove her from the group for her safety. Remove HIM from the group for her safety.
You might find it useful to have a tool such as The X-Card or the Script Change Tool. These both require the participation of the entire group, but can be a handy way to keep players aware of boundaries. I use the latter in many of my games, but I use the former when I run games with strangers at conventions because it's more widely known and easily explained
But, I repeat, your first priority is to assure the safety of yourself and other players.