help!!! traveling to america end of oct-please please read!!

This is very complicated and long winded but please any advice would be so appreciated concerning travel to the US with a uk passport and us visa.

My husband has a US visa due to minor offense he committed in 2001 and we were advised before traveling to the us in 2004 to apply for a visa which he did.
For some stupid reason he did not notice that his passport had a spelling mistake - his middle name spelled ''Leslle'' instead of ''Leslie'' so when his visa was issued it also has the spelling mistake, and we have traveled twice to the us on it and numerous times within Europe.
Now since then his passport expired so he applied for a new one and was told that he would need to keep the old one as the visa was still valid in it, here is the thing the new passport has the correct spelling of his middle name so now his valid passport doesn't match the old one and doesn't match the visa!!
He never honestly noticed the mistake until we were checking passport numbers while booking a holiday to America last night!
He has spent most of the day on the phone to the passport agency, and US embassy london where we got the visa and basically one person says something different to another we want to know for sure that we are not going to get all the way to florida with our children and he is going to be questioned and sent home!!

One person said it shouldn't be a problem, then the passport people basically said they cannot help so phoned the embassy back another person said its down to the immigrations officers discretion! and he phoned back the passport people begging for help and we are hoping to get an official letter stating that it is typing error on their behalf!

Anyone have any thoughts? it seems there is no online help/advice on any website anywhere!

Thanks for reading x