1. bad trips are definitely possible but I have had them mostly for approaching it too casual. Mental preparation is key with DMT, it seems to be more important than what happens during the trip, because everything happens so fast that you take the mood with you with which you started. You should start with nothing on your mind. TAKE TIME to see whats on your mind and deal with all of it before you start tripping.
2. They still do matter, but with other things like LSD it matters a lot what happens during the trip, but considering what happened before the trip you have more time to process it. With DMT there is no chance, no time. So preparation is more important than with LSD.
3. I wouldn't say it is absolutely necessary but it depends on whether you have previous tripping experience and how much you can rely on yourself to correct the direction of your trip. If you don't have a lot of experience get a tripper, but not a random person, get someone who radiates confidence and who is qualified to guide you mentally. That is ideal, if not just get a trusted friend.
4. Some people get fine results with a light bulb but the best way I feel you can do it is use whatever weed pipe like a bong, remove the water, take some choreboy and heat the shit out of it to remove the nasty oils on it, put a piece of choreboy into the bowl of the pipe, put the DMT on top. Gently warm the DMT to make it melt across the choreboy, then carefully smoke it off of the metal. Using choreboy is part of the device called 'The Machine' but I don't find it necessary to use a small liquor bottle, you can use almost anything that can hold the choreboy and has a way to smoke from it.
5. Both, you should hold every hit in for about 15-20 seconds and do your best to take 3 hits. If not possible at least two good hits.
6. Hard to say, the reason for taking the SSRI's in the first place would be a reason to say DMT should not be taken. Will it affect the trip if you still do? It might, results vary from person to person. I have spoken to people who react badly to psychedelics, others get almost no effect and still others experience no difference. THIS CAN EVEN BE DIFFERENT WITH THE SAME PERSON ON THE SAME SSRI AND SAME PSYCHEDELIC. It's unpredictable, recommended against. Just wait until you are fit to get off the SSRIs for valid reasons, wait an extra while longer to stabilize mentally, then see if you feel up for it.