Ok, I made all the changes you described. You can download the files here.
- I translated "GAME OVER" but I left "ON" and "OFF" in English, because there's no way to say it in Greek using only two or three letters. I could have abbreviated the corresponding words but I've never seen something like that before, so I decided to leave them as they are. I'm pretty sure those two are never translated.
- I transliterated "JETPACK", thanks for the suggestion.
- Ok, I left them untouched.
- I translated it. With your explanation, I was able to find the correct word.
- This is a really good idea. I did exactly that, although instead of replacing "WELCOME TO " with a space I used the definite article plus a space ("Ο "), since peoples' names in Greek must be preceded by it.
- I wasn't sure if you meant yes or no, so I just drew them anyway.