I call Google Translate. He's not writing in English, he's writing in his own language and using Google Translate. I can't think of any other explanation. It's just the phrasing that GT gives you.

1) If they seem concerned that their story contains a Mary Sue, then perhaps they are open to some con-crit. Leave a review of the story where you tell them what they are doing right, and what needs work.

2) The Department of Technical Errors is an overlooked group, but they exist for fics like the one you describe. Check out the Wiki page to learn more.

3) Does the author show any improvement in their English? If not, it is probably a troll. Do with that what you will.

First of all, he says that he's writing to improve his English. Didn't quite work, as the language in the profile is so butchered that can only get worse by disabling spellcheck. (And I didn't even understand if he had a dream in which everything in Berlin was written in English or he seriously thinks that someday that could really happen).
To improve English there's only one realiable way: keep studying it, and then exercize writing. Writing alone won't do you any good.

But, as already said, how could you seriously think of writing a fanfiction for a fandom you DON'T know? Heck, I write missions only for fandoms I know really well, and they require a somewhat lesser degree of canon "manipulation" that writing a good fanfic!

Another idea for sporking could be MSTs, as the lenght of the fic is not an important factor as in missions.

1. For this one, I direct you to Spidey3000, a Super Smash Brothers Stu who was slain by the PPC. However, it turns out that his author had come around, and even makes an appearance in-mission. I suggest you ask Neshomeh about this first, but if they seem concerned about their character being a Mary Sue, it may be best to see what their thoughts on the story are then. I dunno how you'd go about asking that of course, but I'm sure there's a way.
   
   2. Well, it still has bad SPaG, formatting, characterization, and stupidity. That, my dear, is what the Department of Floaters is for. Also, if a character is super OOC, then chances are it's a special kind of Mary Sue called a "Character Replacement". So essentially, you go about the mission watching as word mishaps occur while gathering charges against the replacements and other things like that. Basically, you just make fun of the SPaG and the format while going through the rounds and killing off character replacements.
   
   3. My God, you /know/ it's bad when the freaking list of fandoms you're writing for is a wall of text! Miah actually recently did something where she sporked six short fanfictions in the span of a single mission, so you can probably do something like that.
   
   I'm sure someone else has better answers, but... that's my input on it.