That should probably be enough if the morphine is used as the final blow. Not even joking, try to make your CTB place as hot as possible. Serotonin Syndrome causes severe fevers and myoclonus, so go somewhere where you won't be found, maybe a private spa or jacuzzi or even a hot bathtub, and make it as hot as possible while not burning your skin. Stay dehydrated before the session.
I'm not sure if the SSRI and TCA mix will kill, but if you have enough morphine, it should be the final deal. If you get found or you call 911, you will surely be rescued. Serotonin syndrome only has a 12% fatality rate (US statistics) because most are found or don't think to take other drugs to enhance it. Once you are found, you will need to be really lucky to die in the hospital.
This is a very 50/50 chance of you dying or becoming braindead. You might want to go with something else more lethal, but if you need to in a quick pinch, then this might do.