Him calling an election won't make any difference to his leadership of the Tory party, they'll still kick him out, he won't fight the election as their leader
The fear is that if he calls an election and dissolves parliament this will make it extremely hard to force him out.
My guess is that until he loses a vote of no confidence he won't walk.
In the meantime it will be interesting to see if he can assemble a rabble of street activists akin to Trumps gaggle of nut jobs. I don't see it, myself.