A religiously based dietary requirement to not eat pork on the basis of trichinosis does not really make much sense, as the Torah, Bible, Quran could just say “you shall cook the pork well, or you will get the X disease” instead of banning it outright. And as for general health advice, why doesn’t the Torah, Bible and Quran explicitly tell people to wash their hands after doing toilet business (peeing, defecating), before preparing food, and before eating? And at the same time give a simple recipe for soap? Now THAT would be practical health advice. Instead, the Torah and the Old Testament concentrate on presenting detailed prescriptions on how to decorate the priestly gowns and the design of candle holders. Yay.
My wife spent YEARS trying to change me after she became a Christian, she was convinced that if I didn’t “see the light” that I would end up in hell. It took several years and arguments on the subject before I convinced her that I’ve been an atheist my entire life and that I wasn’t going to change.
Razah should try to convince his significate other that even without religion, you can be a good person with morals and raise a family, it can be done. Consider all of the reasons that they’re together as a couple and work on those, if that’s not enough to stay together, if religion has to be a part of it, then it might not work out.
What is the basis of the dietary restrictions in the torah, bible, and koran?
You should ask the author, s/he probably knows.
The blood 
- it was all about blood.
I’ll convene a séance this evening and ask. 
Don’t know about Muslim dietary law, which divides food into Halal (permissible) and Haram ( forbidden)
Going back to times in which there was no refrigeration, I think a pretty good case can be made for not eating shellfish. Also pork, because of the dangers of eating pork not completely cooked. ( Jewish dietary laws of Kosher)
However, that’s not the answer I got when I asked a rabbi at an online yeshiva.
He said: pigs are not eaten because they are a hooved animal but do not chew the cud. Shellfish (oysters, clams, lobster, shrimp) are not eaten because they live in the sea but do not have gills. IE the creatures named are unnatural
This is very simplistic explanation of kosher dietary law, which is around 3000 years old and very complex… Today only Orthodox Jews tend to keep Kosher.
As far as I can see, the basis has to do with purity, which is very common in religious ritual rules. Same can be argued for the Indian caste system, as well as the function of maintaining the status quo***
***my reference; Homo Hierarchicus: The Caste System and its Implications. By Louis Dumont