Oh, you're so close to the end! Those last jumps are fairly tough, I have trouble with them as well.
It might help to think of it like this: the Mothman is connected to the lamp by a spring, so if you can take advantage of the "springiness" you should be able to generate more speed to launch the Mothman.
Here's a gif of one way I managed to do the jump:
Hopefully this helps you (and anybody else) with completing the game, good luck!