DMT might mend the fear of death, might, from what I understand of anecdotal reports. I think it's quite unpredictable how psychedelics will affect you, might as well make you fear death/suicide more, might even make you abandon the idea altogether.
Regarding other drugs, downers might reduce anxiety and anxiousness about suicide that you are feeling, but curing I doubt it.
SSRI's/SNRI's can paradoxically increase suicidal tendencies, especially during start of treatment. I'm on Effexor and it actually makes the thought of suicide so much less overwhelming, but that's just my experience, yours may and probably will differ.