Male ISTP's and female ENFP's seem to be a popular mix. As a male ENFP, I can't really say I understand it though. An ISTP's view of morality, particularly, is deeply troubling for me. I've taught ethics, the standard ISTP approach to whether something is right or wrong is either "there is no such thing", "it's just a hat you can swap and change", "who cares what the justification is, as long as it matters to you". All of which can be hard for the Fi user to accept. This is especially unnerving when you realise that they
do in fact have certain deeply held, but controversial beliefs that they refuse to justify. One ISTP once told me that we should just cull all the senile elderly people and mentally retarded -- because they weren't contributing to society. When I asked him why contributing to society is the be all end all for moral status, he couldn't give me an answer. Another ISTP friend of mine hates movies like Avatar because he
almost religiously believes that that mankind should have dominion over everything else. When I compared his views to racism and asked him to justify the differences, he said "why do we need to
justify something if we already know it's correct?".
The thing is, I really don't think this is uncommon for ISTP's. A complete suppression of Fi, Se-Ni over Ne-Si modelling, being Fe inferior... I think these beliefs are backed up by their stacking of functions.
Look, I'm not trying to pick any fights, nor am I saying that the OP shouldn't date him, but I would never be able to go through with it.