I don't mind the questions at all. It's fun to talk about now and then

Just maybe someone else will stumble across this thread and find something useful (if this is you, you should join the conversation

).
I could explain what ちゃって (
chatte) is, but it would require some prior foundational grammar knowledge. If you know て (
te) form, you'll be in much better shape for this. If you don't, this is gonna be a bit difficult to grasp. So, let's start with a basic verb. I'm feeling 食べる/たべる/
taberu right now, so that's what we're using. You have your basic 食べます/食べました/食べています/etc. Now, you may have noticed that the last example form uses the て form - 食べ
ています. Just a reference, I'm sticking to standard politeness (also sometimes referred to as long form, although it's really a misnomer when you take into account the existence of honorific language) for the moment to keep things a little less complicated.
So, we've got our て form on. We've got our verb. We're eating. Life is good. But wait! That cake... why did we eat that cake?! That was Phakiel's cake! Oh, woe is us! Phakiel is gonna be so mad that we ate the birthday cake he smuggled out of an acquaintance's party. However shall we explain this to him? We
totally ate his cake and it was
good. What else can we say?
食べてしまいました!(We totally/completely ate it [perhaps even regrettably]!)
Broken down, this is 食べる in て form --> 食べて, and then we use the grammar pattern referred to as 〜てしまう --> 食べてしまう, which we then turn into standard politeness past tense (that cake is long gone, after all) --> 食べてしまいました!
We're ever so sorry, but that is just way too much trouble to say for how little we honestly care. After all that delicious cake, I am feeling pretty damn lazy. I'm not bothering with all those syllables. Screw that! He can take his apology in short form!
食べてしまった!
You know what? That's still kind of a lot of work. That cake was too tasty to feel bad about eating it. It's time to pull out the slang with an insincere apologetic look.
Here is where it gets complicated (I did warn you by saying "slang" was coming). 食べてしまう can be shortened to 食べちゃう. This is the short form of a slang version of 食べてしまう. Just remember that they are equivalent and the rest will get a lot easier. Once again, 食べてしまう=食べちゃう. Got it? Maybe? Good enough. Moving on to the end!
Phakiel, we have something to tell you, man. ケーキを食べちゃった。There, we said it. We are pretending to be sorry, so get off our backs already. Sheesh.
Don't worry, I'm done with that horrendous story

What you saw as 〜ちゃって is simply the て form of the slang version of 〜てしまう. It means to do something completely and, depending on the context (like all Japanese things), it can also have an added layer of regret. Maybe you read a diary. You could read a diary completely and have no feelings of remorse over it. It could be a diary from the school library you were reading for a class assignment. On the other hand, you could have just read your little sister's diary and she will not be happy with you. Both have the option of being expressed with this 〜てしまう form.
I'm starting to feel like I'm the master of too-much-information. I should cut myself off here >_> I hope that wasn't too disjointed. Let me know if you'd like any clarification.
Woops, almost forgot to address part of your post. I continue! あなた and any other form of "you" is rude in most situations. There aren't a lot of times when it's a normal thing to say, so stay away from it. I still have not used it much. It's a land mine waiting for you to step on it. Don't.
As for the kanji and homonyms junk, it's not as bad as you would think. In fact, it's really not much of an issue most of the time. The context is key. If you don't know what a person is talking about, forget about it. If you do know the general topic at least, however, you are much less likely to have difficulty understanding which version of a homonym they are using. It's kind of hard to believe until you see it in action for yourself enough.
Now, as for the accents part... That one is a bit trickier. There are indeed words that sound the same aside from the intonation (high or low) and have totally different meanings. It is important, but it is not necessary most of the time to communicate. There just aren't that many words where it really matters in my experience. Most homonyms, however, have the same basic intonation. It's all about the context.
For real, cutting myself off!