Vanilla: Bomb Collars explode after 10 seconds (15 with Christine)
This mod changes the Bomb Collar timer to 100 seconds (little over a minute and a half).

Vanilla: Toxic Cloud reduces HP by (Players Max HP /40) Per Second
This mod reduces that value to (Players Max HP /400) Per Second (10% of the original value)

It might not sound like much, but it has a huge effect when ingame. If you would prefer different values than provided, the GECK can be used to change the variables to increase or decrease the difficulty.


Warning:
I have tested this mod using multiple gamesaves, but have not done a full playthrough with. Also note that *if Elijah gets pissed off and decides to set off your Collar manually, this does not change the timer on that. It'll countdown normally. (Those that have completed this DLC will understand what this means). I sat by a speaker until the Bomb Collar exploded, and it took a minute and a half. I sat in a Toxic Cloud for a minute or so, and only lost about half my HP and the visual effects functioned normally. I'd be interested to see what other players experience, or get feedback about how well this works. IMHO: it breaks the functions of the Bomb Collar and Toxic Cloud to my satisfaction.


Requirements:
Dead Money DLC

Install Instructions:
Simply place the "Dead Money -BmbClr&ToxCld Relief.esp" file in your Data folder and enable in your Mod Manager or equivalent.
Mod Order: Doesn't matter, just needs to load after Dead Money. Should have no effect on any other mods unless they also alter these 2 specific scripts. My suggestion: put it last in your order, and only activate "Dead Money -BmbClr&ToxCld Relief.esp" when you play through Dead Money, then deactivate it after you return to the Mojave.
Also Note:
Can be added to your mod order and activated mid-stream through the Dead Money story, or disabled at any time. It does not effect gamesaves. Achievements are still possible.
However: if you started playing through with a different "Collar/ToxicCloud Remover" mod, you may find that disabling your old "Remover Mod" re-activates speakers that cannot be deactivated at that point due to terminals already having been used (with the scripts governing them absent). The terminals can't be used twice to deactivate speakers, so they are "perma-on". I highly suggest you use caution when playing through with "Collar/ToxicCloud Remover" mods. They may work as advertised, but might have script breaking side effects.


Details:
If you're like me, you played Dead Money the first time, and it was all new and exciting. You beat the DLC, and moved on in the Mojave.

Then you restarted the game, and went back with a good idea of how you'd tackle the content the 2nd time through. However, the constant head exploding is now old, Really OLD. It's become annoying, and it doesn't enrich your playthrough anymore.

You may have even tried some of the mods that eliminate that aspect of the DLC completely (as I did); only to find that it broke the scripts that allow the DLC to advance through all the quest stages properly.

I looked through the mod I was using, and it was a hatchet job of flat out eliminating script references all over the place. It works as advertised; sort of... except the quest "Strike Up The Band" won't update unless you disable the mod, do the last stage, then save, and reload with the mod enabled again. Many of the speakers were not disabled by the computer terminals, and other issues arise from the scripts being "butchered" out by the mod.

I sought a more elegant approach that does the job of "breaking the game" without removing any of the scripts. I simply monkey'd with the math that calculates how long before the Bomb Collar explodes, and how much damage the Toxic Cloud delivers each second. It's even adjustable to your own perference if you're familiar with the GECK:
Three simple edits to the algebra governing these values:

NVDLC01BombCollarQuestSCRIPT:
Changed 2 "GetSecondsPassed" references to (GetSecondsPassed * 0.1)

This changes 10 seconds to 100 seconds. You can use the Geck to edit the values to your own preference: changing the value to 0.5 will give you 20 seconds; change the value to .25 will give you 40 seconds.
The Beeps on the collar are very very long, and speed up as intended to short quick beeps when you near 10-seconds left.

NVDLC01ToxicCloudTriggerSCRIPT:
Changed 1 reference "(PlayerREF.GetBaseActorValue Health / 40)" to "(PlayerREF.GetBaseActorValue Health / 400)"

This changes the value of how much damage the Toxic Cloud does per second from 2.5% Per Second to 0.25% Per Second (10% of the Vanilla Damage Value). You can use the Geck to edit the values to your own preference: changing the value to 80 will give you 1.25% Per Second (50% of the Vanilla Damage Value).


Disclaimer:
I have no idea if the scripting math is "rounding up" to Integer values at any point in the calculations, or if it's freely using the Absolute Decimal values when it finishes it's calculations, but from what I experienced in the game, it seems to be working as predicted, and the result is pretty obvious.

Have fun, and I highly suggest using the Underground Hideout mod with the Teleporter for the Dead Money ending: It has a nice place for the loot :D. You can craft it's Teleportation Device at the workbench in the Villa:
http://www.nexusmods.com/newvegas/mods/37884/?


I'm not going to claim any type of Modders Copyright to this, it's just a script edit that anyone can do, and not worth claiming ownership over. Have fun with this.