I think you may be interested in revisiting my “So I sat on the couch determined to not do anything for next 5 minutes” in Syd's PCE Log
It is interesting you describe this basic fear as being not only about survival but also reproduction (sex & bonding). My December panic was largely of the later kind. But the great thing is that, once the “simple” core passions (past the head and heart activity) are acknowledged, you can sit with them until automatically coming through to ‘the other side’ (sensuous & naive enjoyment), sometimes even a PCE may result sooner or later … even though sorting out its implications (see last paragraph below) will take some time.
RICHARD: […] fear is both the barrier and the gateway to the actual world. There is nothing so thrilling as a trip through fear … and then one comes out the other side. There is no fear here, in this actual world where I live. Not even disquietude, uneasiness, nervousness or apprehension … let alone anxiety, angst, fear, terror, horror or dread.
It is not a case of ‘facing fear’ … one can use it to swing through to this actual world … leaving one’s ‘self’ behind, where it belongs, in the ‘real-world’. Selected Correspondence: Fear
Edited to add: Regarding “the fact there is a lot less potential life ahead, than there is behind”, yes that’s part of the sacrifice necessary to coming to be here more as a sensate body. 
Can you be completely happy (as well as harmless with the opposite sex, as in appreciating their preferences & choices as well as wishing well) with the potentiality of sex & bonding, for instance, never happening again? FWIW, it was a similar consideration (“going about it on my own”) that lead to my last PCE. But I do find the question posted before to be going straight to the nub of the issue more than my consideration. There’s a cheerful death of the sexual identity imminent.