I recently bought an Egyptian contract FN-49(8mm), and haven't been afforded the opportunity to really shoot it, but with the few rounds I did put through it, the brass was thrown nearly 40 feet!  Should it do that, or might this have something to do with a need to adjust the gas flow?

And one more question: What the hell is that little lever/button/switch on the upper left side on the forward end of the reciever cover?

You have too much gas driving the piston.  Adjust the gas regulator immediately and do not shoot it extensively in current gas setting as you will accelerate the wear and tear of the gun.  To adjust the gas regulator, remove the front hanguard.  First you need to unscrew the nose cap, slide the cap forward, and the front handguard should be free.  Immediately to the rear of the gas block, there is a round steel sleeve that you can rotate.  This is the gas regulator.  It works by controlling the size of gas bleed port exposed.  Larger gas bleed port = less gas driving the piston, and vice versa.  With your current setting, you need to turn the regulator to the direction that increases the opening on the gas bleed port (you can see the port).

The lever thingy on the left side of the receiver cover is the manual bolt hold open.  So you can hold the bolt open with partially full magazine.  Just retract the bolt back, push the switch and gently release the bolt forward.  You'll see.

Forgot to add this ...

What ammo do you plan to shoot out of this gun?  Most 8mm ammo out there are corrosive.  Make sure you clean everything.  Including the gas tube, piston, gas regulator, and inside the gas block.  

Also, Turkish 8mm ammo (comes in stripper clips with bandoleers) does not have the right pressure curve for 8mm gas operated gun like the SAFN.  Do not use the Turks on your FN49 if you want your gun to last longer.  Yugo, Greek, Romy ammo are OK ... the incredible ejection distance you saw could be caused by the type of ammo you shot.  Was it a Turk?

Thanks for the help.  I've heard enough about Turk to know to stay away from it for self-loading rifles.  The ammo was some eastern European stuff, made in '74(or so I recall), and the cases looked like laquered steel(metallic green/OD).

Sounds like you have Romanian ammo.
They are OK, except that FN49 was not designed with steel cased ammo in mind.  Shooting steel cased ammo out of this gun may be hard on the extractor.  Once you adjust the gas regulator I think you will be fine pressure-wise.