So, for the foreigner approaching the lands of Minecraft, let me quickly summarize danger levels:
Highly dangerous: The surface at night. Monsters will spawn everywhere and swarm you from all directions. Skeletons will pound you from range, with little recourse. Hell. Fire and cliffs everywhere, horrifying hordes of screaming, sword wielding beasts that will mob you if you look at them askance, while swarms of giant jellyfish float (sure, they're slow, but they're far away, and don't need to chase you around (and indeed, keep their distance, and cannot be run down on account of floating over magma seas or vast canyons), since they can just set the ground on fire and blow it apart, hindering any work you may be doing in hell) around the massive caverns, screaming and spraying fireballs in your direction from well outside bow-range.
Moderately dangerous: A pitch-black tunnel in the bowels of the earth. Monsters can only attack from a few directions while in a tunnel. You have nowhere to run, and monsters often fall from concealed chambers above. Dead ends can be lit up, limiting the number of approaches for newly-spawned enemies. Lighting is no longer as effective at stopping spawning in the depths, so be prepared to use lots of torches to stay safe.
Minimally dangerous: The depths of Hell the Slip the Nexus. The only hostile mob is huge (and therefore limited in where it can travel), slow, and its attacks are easily dodged. (It is also vulnerable to lava falls, bows, and fishing rods + melee weapons!) Pig zombies are completely passive so long as you do not engage them. The surface at night. You can just sit on a small island or go for a swim till morning, even if you have no light.
Does anybody else find this incomprehensible AWESOME AND HILARIOUS! exactly as it should be?
Fixed.
According to the wiki, ghast fireballs are too weak to break cobblestone, so safe encampments in hell should be possible, if you can get them built before a dozen ghasts spawn within sight of you and turn the entire staging area into a pitted inferno (yeah, one or two is harmless, if annoying, but once they get up to half a dozen or more, all screaming and shooting at you, you can't just dodge anymore, because the entire area nearby is quickly coated in flames, and torn apart, making it increasingly difficult to escape). Having a safe cave nearby that you can dive into for a while might work, they seem to wander off or despawn after a while of being unable to see you. Just be sure to have no internal spaces large enough for them to spawn in (assuming they don't require darkness to spawn).
And the weird problem with new normal-space gates being formed on returning from hell is almost always caused by the fact that gates won't be placed in open air, and so instead move to the nearest acceptable location, which, on returning, can't find a gate in its designated chunk, and so assumes it's a new gate and makes one in the right area, fucking over any plans to build a coherent network of gates. It would make far more sense for it to make a floating cluster of red cobblestone for the gate to sit on if the chunk corresponds to open air in hell, and to create a bubble of air around the gate if it would be otherwise buried. Considering there seems to be some kind of "closest to" algorithm already selecting it, making a borehole through to the nearest open air would probably be a trivial thing to code, if the idea of just having a buried bubble of air with a gate in it isn't suitable for convenience reasons or some such nonsense.