Broth
Normal liquid - you do NOT want him to get dehydrated - you WANT him to use his throat. If he doesn't get it going - it will take longer to heal.
Yogurt
Mashed potatoes
Jell-O
scrambled eggs with cheese
he can eat whatever he wants to be honest - he can decide what hurts. The longer you "baby" him and such - the longer the process will be. I know that sounds cold, but it's matter of fact, the faster you get your throat to working like usual/normal - the faster you recover....and attitude...attitude is EVERYTHING!! If you keep positive and stress the good things that will come from this - positive attitude kicks butt in healing process!!
Yes, it's okay for him to lay down. He does not have anything impeding his breathing - correct? No gauze up the nose, right? BE NORMAL! ACT NORMAL!
Sleep is good for healing as well. Gives the body a chance to recuperate as well.
Cannot stress enough the fluid intake!! Keep that going! You do NOT want him to dehydrate!