You don't have to ask me, knowledge is meant to be accessible for anyone.
Indeed 255 is the maximum value, in fact in MindCrystal Vitamins give 15 EVs in their respective stat and cap at 255 EVs.
In CrystalTile2, click Ctrl+N to open the file browser, go to file a/0/1/7 then right click and click "Sub-file Sort…", this will open the sub-file browser and this is what the term "File" actually refers to.