I've got a thread here on Radioactive Iodine Therapy
Jake will need to stay in clinic for a week for the treatment, usually treatment is administered either once or twice depending on how high the T4 and the rest of the week is to give time for the radioactive iodine to be mostly eliminated before going home.
Once Jake gets home for about a week you will not be allowed litter box duty - your husband will have to take care of that while wearing gloves. Jake is also not supposed to sleep with any family member or have prolonged close contact ie 3-4 or more hours of him sitting on someone's lap etc for a week as he will still be shedding the radioactive particles in his urine, saliva etc for that time.
When Duffy had the procedure she came through it like a star & she had an old t shirt I had slept in for the week prior with her in her cage (it doesn't come home they toss it) & a couple of toys from home. The Drs let the cats out for playtime every day & give updates on how they are doing, what toys they like to play with most etc.
As for food like SCM says high quality protein is best Wellness is good as are others she's mentioned, especially since at this point he might not even have CRF