i could solve this for you in like 2 min if i still had my steel book from school. Using the values your friend calc’d, assuming he’s doing it correctly, you can look through the tables in that book to find a 5" beam that should fit what you need, if its not in that book it will have to be a custom beam which is going to be big $$$$. Just make sure your friend knows what he’s doing with those calcs, i’d bump up the original weight to an even 1500 #/sqft just for a little added safety. And are you 100% sure that beam is only going to take load from half the house? This isn’t something you’re going to want to guess on unless you’re willing to risk your uncle’s life.