You should'nt have problem with loadVariable actions. When you use it into a button, code like this :
Will load the file into the clip that embed your button (into _root if your button is placed directly on the stage). Then at the end you should have your loaded variables defined where you loaded them. You also can load your variables elsewhere by applying the action to the recipient clip :
will load datas into the _root.mc1 MovieClip.
I had at a time some problems with multiple concurent loads and it happend that some connections get lost. If it is your case, try to load your different files one by one. Use for that a clip that will trigger the data event to know when you can launch a new load.
Hope it helps,
Oh Lord, shut me down !