Sorry for your problems, its never good to have a horse in trouble like that, I had one die on me about 8 months ago and I know how it feels to stand there helpless not able to do anything. I doubt you need me or anyone else to tell you that options numbers 1, 2 and 3 is to get a vet there fast, but, if you are looking at a dead horse and no vet type of situation and nothing to loose well here’s what I can say.
There are a bunch of things that are called colic, so I don’t know if what I can say will be any good, however I have seen my uncle, who has been breeding horses since before I was born, save horses from, I think sand colic maybe, by getting a garden hose, a jar of Vaseline and putting the horse in a stall or something, something where it can't kick you if you are behind it. Lube up the garden hose and stick it in its bum, stick it up there a fair way, and gently turn on the water. It will flush out the horse. I saw him save a few like that.
The other one I saw, and I have no idea how or why it works, is what I saw the Bedouin I lived with in Jordan do with horses that couldn’t pass faeces or urine. They would get a big can, .like an old 10 kilo flour can, it has to be metal because you need to light a fire in the can, and pull the lid off. They would then start a small fire in the can, just start it with a bit of paper and some twigs, but a pretty good little fire. They they would get a few hand fulls of date seeds and put them on the fire and get them burning. They smoke up pretty good, and once they were producing smoke they would cover the top of the can enough to catch a heap of the smoke but not enough to put out the fire. Then they would get the sick horse and force it to breath in a heap of the smoke, as much as possible. They'd do this a few times, the horse didn't like it, but they’d twitch it or something and make it breath in the smoke. Once they had done this, they’d keep the horse moving, even trotting if they could make it. Usually within 15 minutes it'd loosen everything up and the horse would come good. I guess there must be some chemical in the date seeds that gets released through burning and absorbed by the horse's lungs.