1) Think more along the lines of "This is so bad that I've forgotten how to swear." Really any flavor text would beat the current descriptive "Lava pours out of the floor." or whatever, I just think understatement would be funnier in context.
2) In other words, "It's not a problem that arch-viles spawn on level 2, if you don't want to die, just don't go to that side of the map!"
The potential benefits of levers should outweigh the risks or else they're not worth using, and this is a balance issue, not a "you're playing wrong" issue. I don't have a problem with levers being risky, I have a problem with them killing the player without warning or escape. Later on, lava levers can be escaped with a phase device, or a large medpack, or an envirosuit, or just having good boots, so they're an expensive risk but usually not fatal. Pull a lever on level 20, you might have to spend one of your large medpacks, or you might get your power modded red armor repaired to full. On level 2, you might gain 10 hp, or you might die. Not exactly comparable risk versus reward there.
I don't see a problem with acid flooding levers at any level, or lava flooding levers after protective items start being generated. "Flood whole level" levers are fine too, because you know exactly what you're getting into there.