I'm wondering if you could sub Worcestershire sauce for the fish sauce. Isn't that what Worcestershire sauce is supposed to be - sort of?
Not a chance. Worcestershire ("Wooster") sauce is indeed Asian, but it's a sauce with its own real flavours. Fish sauce is an MSG-heavy condiment, like greatly-amplified salt. I use it in everything, including ice cream, with no complaints.
Take a deep breath, and embrace that funk!
Addendum: I've actually made fish sauce, without realizing it. I did fisheries research on the Hudson River for the NRC, monitoring the effect that the Indian Point nuclear power station was having on fish. It was the greatest job in the world, swanning around in fishing boats all day, except that we also had to count every last fish that the water-intake screens killed.
In the summer heat, they piled up several feet high on the sorting tables. If we didn't get to them quick enough, a disgusting thick brown stinky fluid would exude from them. We called it "mung" and tried to keep it off our clothes. That's a fair description of fish sauce. (Oh? Did I put you off?)