My boyfriend vomited 5 days ago from what he thought was food poisoning. he was fine the next day, but i have not seen him since. would it be ok to kiss him after being symptom free for five days, or would the virus still be in saliva?

Food poisoning is from a toxin in the food, not a virus, though symptoms can be similar. There is generally no fever with food poisoning, but is with a virus. If it was a virus and the fever is gone for a few days, it would be gone from his saliva.

If he has free of symptoms for five days, there is no risk in kissing him, even if the "food poisoning" was due to a microorganism.