the first "strike" is present on my account, but I don't understand for what reason.

The enforcement team are the only ones who handle suspensions and they do not use the forums so no one here would have that information. All we can suggest is to read through the Community Standards to maybe see if there's something you may have missed. Suspensions are also not always issued the same day the action took place. So it could be for something that happened days or weeks ago. It also doesn't have to be for something done online in a game. It could be something on your profile or maybe an LFG post or something like that.

World War II. I understand many gamers are burnt out on it, but believe it or not, the first WWII game for me was CoD:WaW. Loved it, as I'm just more interested in the era. For some reason, games set in present day just don't hold much "escape" value
for me.

Haha... this is hilarious. You know what's funny? You don't understand that staking out a dead body to kill someone that just got a kill is what's going to run rampant in this mode. This game type endorses camping and punishes those who strike first.

You would need to post here to find out why you had to change your gamertag -
forums.xbox.com/.../41.aspx They are the ones who handle those issues.

whether you agree with the PET's decision or not, the fact remains that you must change your GT before you will be allowed back online. As I said earlier, make sure to change it to something sensible or you will find yourself in this situation again.