Why did he continue the hit?

He had a few stolen identities in his sleeve he could use any time, and although he knew these identities would eventually be discovered, he relied upon the time factor. It would take days to the police to track those identities down, and then no one else but him knew exactly where he was going to kill De Gaulle and when. Also, leaving the job undone now after having cashed half of the fees he had asked for, might make the OAS to track him down later and kill him for having failed.

The movie may have become too short - and unfinished business is there to haunt.

Ilania Abileah
Artist, and Culture Reporter

It's explained in the book. This was going to be his retirement job. $500k in 1963 would be worth between $3M and $12M depending on how you calculate. He wanted to retire into a life of comfort (he may have had some other money saved too.)

He thought about taking his $250k deposit and running, but then the OAS would be after him. And even if he gave it back, the French government was on his tail now - with de Gaulle dead the OAS in power, that would stop.

And he really thought he could stay a few steps ahead. He had a couple of identities that he didn't think they could trace in time.

as another post said you can see when he stops at the fork italy/france roads he is thinking of bailing and he basically says screw it i'm doing it. i think he realized he was screwed if he stopped, the french would keep hunting him even if he bailed on the job and he would be too well known to keep working (every passport control station in europe would know his face) but he didn't have enough money to retire and hide out the rest of his life. so he decided i either finish the job and have enough money to hide and live out my life, or i fail and die.

I wondered the same thing. There was no way he would ever get paid the second half of the money even if he did succeed, so why didn't he just bail out?