Find out from the lawyer if the decedent was given conformed copies of the will along with the original. The grandfather should not have been given access to the box if he was not a signatory. A probate lawyer is probably needed.
If there is no Will the surving spouse gets the deceased's estate.
Presumably the Will names the spouse as executor, no?
So the Will must be filed with Probate and your boyfriend has 6 months time to file a contest on the Will in the county courthourse. I think he should hire a lawyer and have the lawyer on law firm letterhead write to the executor that the Will of the deceased should be put in for Probate on the boy's father that has now passed.
Because you are quoted from the Will, I assume someone has a copy of it. Under certain circumstances, the copy of a lost will can be admitted to probate.
You boyfriend needs to meet and hire a probate lawyer as soon as possible.