If you can not untangle the halyards, then pulling them out and starting again may be your best option. A plumb bob or some type of messenger such as a few links of chain works well. I would not use a snake because you do not know the path it takes as it descends down the mast.
Two things to consider:
One, make sure you can pull the halyard out without it fouling inside. This could be a big pain, and you may end up with the mast horizontal again. As you pull the old halyard out tie a tag line to it so if it does get stuck as it goes up, you can pull it back down again and try again. If you need to pull the halyard out from the bottom end you will really need to use a tag line in order to keep all the line from dropping down at one time and causing a big problem.
The second thing is to make sure the halyard ends up on the correct side of the through bolts witch secure the mid stay tangs. If the halyard crosses over and rubs against them they will wear prematurly.
If you have a forward steaming light try popping out the fixture as it may be fouled at this point. You may be able to inspect the line and grab it with a bent wire . I assume you have internal conduit for the wires. If not consider it. It may be the overall problem.
Good luck, and let us know how it turns out.
