Labyrinth, one amendment to your first paragraph which is mostly correct, mlvl = area level only in NM and Hell. In Normal, monster keep their mlvls assigned in the game data files. I'm not aware of anywhere online that lists those, I'm afraid. It is unusual to want an item with a specific level that low though.
To answer your question though, the parenthesed values on the Prefix/Suffix pages are
alvls or affix levels. As they are (a) often wrong and (b) not necessarily updated for 1.10 and (c) alvls aren't explained there at all, it does indeed elude me why they went to the trouble
You can probably find a more comprehensive explanation of alvls elsewhere on this forum, but for the exact answer I like this page:
http://www.diabloii.nu/affixcalc/alvlcalc.html
Basically an item's alvl is worked out from its ilvl, for low-mid level items it will be ilvl - (qlvl/2) where qlvl is the qlvl of the base item (can be looked up on d2data.net). For high level items it changes to ilvl*2 - 99. But to understand it precisely you need ot follow the code in that link.
Oh, and the top Vita suffix is indeed impossible. No matter how many people tell you otherwise

The highest alvl an item can have is 99.