how did jules and vincent survive seinfeld's attack?

Jules believed it was divine intervention.

Jules was spiritual.

I don't think it was "bad writing".

First of all the bullet holes were on the wall before Seinfeld came out of the closet. Now as to how they survived I doubt it was divine intervention, either the guy was a bad shot or he accidentally loaded the gun with blanks

Seinfeld's aim was off because his gun-toting hand was debilitated from endorsing thousands of checks from the Super Terrific Happy Hour. He had Super Terrific Carpal Tunnel Syndrome.

Because Jules and Vincent didn't even flinch.

Seinfeld's aim wasn't bad, just that his brain predicted that they would duck for cover or AT LEAST flinch!

But they stood like a stone statues...with stoic faces that showed no surprise to boot. This naturally counteracted Seinfeld's predictive aim that would have killed normal assassin's with lesser moxie.


OR

Because Jules and Vincent showed no fear of impending death, this put a serious whammy on Seinfeld's aim.

It was a miracle and that’s why Jules quit to Walk the Earth.

But remember there are point blank gunfights all the time where people dump whole mags and don’t hit anyone.

pulp: : a magazine or book printed on cheap paper (such as newsprint) and often dealing with sensational material also : sensational or tabloid writing —often used attributively

Not God. The Devil. Marcellus had an arrangement to get whatever was in that case delivered to him. Because of such, Jules and Vincent got to live. Crazy ass Jules, having a rub up against darkness, flip flops the other way and runs to the Lord.

I literally believe it was dumb luck, but Jules took it as a sign and Vincent just treats it with indifference just like he does with other aspects of his storyline which inevitably gets him killed.

The message I took from this is that Jule's self-awareness transforms from that of a criminal to a spiritual seeker. He has lived his whole life committed to executing evil acts on behalf of his employer but now he sees that he has been in the wrong. Vincent's only care is making money to pay for his heroin addiction.

His heroin addiction ultimately leads to his death as he is constantly constipated and in a critical time when he was suppose to subdue Butch he finds himself grappling with his bowels. On top of that, his lack of self-awareness results in him leaving his hand cannon on the kitchen counter.