If you are really paranoid about the handle coming off of the 788 (they are screwed on, with only a few threads), then just get rid of it. There is no point in feeling worried about your rifle, when there are literally hundreds of others to choose from. Its just a hunk of metal parts, not a person.
On the other hand, I have never heard of a handle coming off a 788 when it is shot with factory ammo only. I have a suspicion that in the vast majority of cases, the handles come off as a result of folks shooting handloads, which create the necessitiy of very hard yanking to lift the bolt (even hitting it with a mallet), to open the bolt after a split, stuck or overloaded round.
Regards, Mannyrock