Is it worthwhile taking the DMZ tour?

Any information will be appreciated, but I'd especially like to know the following:

what days does it run?
is it safe?
are you allowed to take pictures?

It depends on who you are going through for the days it runs. The USO has tours on the following dates in February: 2, 5, 9, 14, 16, 21, 23, 26, 28 & 29. You can book the tour at the USO on Camp Kim near the Korean War Museum. You do not need a SOFA ID to enter that USO.
The cost is ($44/person) and due 4 working days before the tour day. In terms of payment, you can pay with either cash, check or credit card( US VISA or Master Card only).
The tour departs at 0730 and usually gets back around 1530hrs.
It is safe-ish. Incidents can always happen, but they have not happened for many years. I would say you are more likely to be killed at Lotte World than the JSA.
There is a dress code for the JSA, but there are other DMZ places where there is none. I have been to four of the seven visitor centers across the peninsula, sometimes officially sometimes as a civilian, and been specifically to the JSA 5 times. All of them are worth going.
The tunnels are interesting, but if you have been in a mine shaft you already know what they look like. With them it is more the concept that is interesting rather than the actual visit.
You can take pictures in designated areas of designated things. Do not play with this rule. You might lose your camera.

Lol I was stationed at the Imjin River when I was in the U.S. Army, however I never went on a Korean tour. I know you are allowed to take some photos, but at the Demarcation line you are not. It is quite safe and I know they will take you in the hidden tunnels North Korea had dug in the 70s and 80s almost to Seoul. Including the building where North and South Korean government officials sometimes meet and sign federal documents.

Yes. Tours varies by company. Yes, it's safe. There are restrictions on when/what you can photo. The tour guide should be able to answer this. Try the East coast, near the Sorak Mountains.