"Elk pak is van mij."

With the exception of certain idioms, 'elk' and 'ieder' are interchangeable.

i think it should be every suit is for me, and every suit is mine would be "elk pak is mijn". im not sure though.

Same

It is my understanding that ...

"Elk pak is voor mij" = "Each suit is for me.

I think there is no "mine" in Dutch. Likewise, no "hers", "his", "yours".

It is hers = Het is van haar.

It is his = Het is van hem.

It is yours = Het is van jou.

Same here.

the mouseover translation says any.

Elke is every, enig is any. If it were "Enig pak is van mij" you would be correct.

The difference here is you purchasing EVERY suit, or ANY suit. If you purchase ANY suit you are not purchasing all of them, however if you purchase EVERY suit you would be purchasing all of the suits .

Adjectives that modify a noun like "elk" get an extra 'e' at the end in most situations. It's not complicated but difficult to explain completely:
* either a "de" or "het" word used with a definite article gets the 'e': "het rode huis" "de kleine baby"
* A "de" word used with an indefinite pronoun gets the 'e': "een kleine baby" "een gezellige avond"
* A "het" word used with an indefinite pronoun gets no 'e': "een rood huis" "een lang boek"

that'd be "voor mij"

no, all suits are mine. :D

That would be 'alle pakken zijn van mij'.

Pretty much, however there is some times where it's not, mijn vriend can mean my boyfriend, whereas de vriend van mij only means the friend of mine.

'van' is used to indicate possession. The literal translation would be 'every suit is of me' (but 'every suit is mine' sounds better in English I think...).