I haven't downloaded the file,because at some point you will have to do that yourself,but i can explain how to pass the wi-fi check.
1)PID :
You said that you've changed IV's and EV's only,but not all natures can be acquired if you have all 31 IV's,some natures need less IV's in a certain stat.
So first of all go to PID put "=" sign(read the pop-up tips) near the most important(to you)stats,choose the nature you want,put "either" in "gender" and in "ability" you must first check how many abilities your pokemon has and which 1 of them you want,so for example you have a pokemon with 2 abilities and you want the 2nd ability,so put "2" in the Ability tab(any Pokedex-like website will show the abilities in the correct order).
Uncheck "Shiny",and click search,choose the PID and click ok.
Note : Dream World abilities will not work.
2)Nickname : Read the "Correct Way to Name your Pokemon" topic,as Codr posted.
3)Country : Japan
4)Origin : Black or White(W/e version you have),unless you want something like a scizor with bullet punch and superpower in this case put diamond or pearl.
Lets Switch to the "Met" tab.
1)Location : Choose Sodateya Fuufu(DayCareCouple),unless like i said you want something like a scizor with bullet punch and superpower,in this case put "(PokeShifter)".
2)Ball : Pokeball
3)Level : 1 for DayCareCouple,100 for Scizor with Bullet Punch(just an example,can be any pokeshifted pokemon).
4)Date : Leave it as it is.
5)Encounter : For Both cases pick " Egg/Pal Park/Event"
Do not touch "Fateful Encounter"
6)Check "As Egg" Only if you picked "Sodateya Fuufu" in "Location",if we're going for a scizor with bullet punch,skip steps 6,7 and go to the "Stats" tab.
7)"Game" will either be blank or "Black/ White",just don't touch it,it will work even if it's blank,for "Location" pick Route 3(you can pick any location you want).
The Stats :
1)As I'm sure you know you can only spend 510 Ev's in total,no more than 255 each stat,when finished with EV's go to the "Attacks" tab.
Attacks :
1)First of all the reason i used scizor as an example,is because bullet punch can't be learned in Black and White,in which case if you "hatch" your scizor in black and white and put bullet punch on it,the random wi-fi will reject it,as you can't have a bullet punch if you raised it in B/W.On the other hand the WiFi will gladly accept a pokeshifted scizor,you have to "pokeshift" any pokemon that can't obtain 1 of the Diamond/Pearl/Platinum only moves.
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Pokemons that weren't hatched but have 1 of their egg moves,will be rejected on Random Wi-Fi,which is why in my explanation it's either Pokeshifted or Hatched.
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After choosing your attacks go to the Last tab "OT/Msc"
"OT/Misc"
1)ID's/OT : View the Data of one of your legally caught pokemon and copy/paste the Data from there.
Don't touch anything else,just save your pokemon and it should be perfectly acceptable on Wi-Fi.
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P.S.
If you want a B/W Event Pokemon you need to know the Exact Location where you can find it and the exact Level when you encounter it(If you don't know,youtube is the best place).
Example : My "Legit" Randorosu(Works perfectly fine on Random Wi-Fi).
Location : Fertility Shrine
Ball : Ultra Ball
Level : 70
Encounter : Egg/Pal Park/Event.