PS You could also teach him to share his toys when he is at home, is it possible they could make it less hours children need their parents a lot at this age.How old is his brother if he is older is he kind and not causing any upset with him.Perhaps as he had his tonsils out have him checked His throat could be sore.
Possible that he doesnt get enough stimulation there ,do you know if they play games and read and do other activities with the children?Again, lots of Fun and Games and sports with Dad getting involved and check out the day care do their part.
he is going to daycare ... longer hours than normal for some work reaons.
he's gotten better.. maybe something was bothering him.
He says he doesn't like going to daycare due to the other kids touching his toys.
When you say recently this started happening, had there been any stress going on in his life , any new Dramas.How is your interaction with him and is there a Dad around,Have you asked him if he likes Daycare and what he does there, are there enough activitys so he is challenged enough for a 5 year old. Get him running and playing Ball and using up energy, if Dad is there ask him to participate doing guy things.Does he go to Daycare for a lot of hours could they be cut back so you could have more time with him,why does he take a Nap at 5 year old?
You're dealing with anxiety - perhaps social anxiety. The fact that your son is able to function most of the time at school is very good - he probably just requires a bit more patience and understanding. The "not speaking" is called "selective mutism" and I'm assuming that these episodes are very short in duration. All of the other parts of your post indicates anxiety - possessiveness, over-reaction, crying, tantrums, frustrations, social issues, sleeping issues (and probably toileting problems which you did not mention). I suspect his recent surgery heightened his senses and this has caused an increase in his anxiety issues. By the way, if anxiety is the issue, your son is not able to control his emotions (so talking, punishing, bribing, etc. will not work) - his anxiety is doing this and your son may need help to learn how to "manage his fears".
I might suggest you google the term "childhood anxiety" or "selective mutism" (although I don't think your child's anxiety is this severe form of social anxiety - but this site "selectivemutism.org" should give valuable information in the "resources"section on how to deal with some of your son's issues) or perhaps other phrases similar to those I used. The best thing that you can do at this time is to educate yourself on this problem and then to remove as much pressure and stress you can from your son. By the way, anxiety is a very common problem and your family doctor should be able to give you advice on how best to help your son (or a referral to a medical professional with experience in anxiety disorders). If anxiety is the issue, I assure you your son will not outgrow this nor will it go away; but the earlier the diagnosis, the better the prognosis. I wish you the best ...