but on the other hand I sort of want Bruce to smack Tim and say, "You have a chance to be with your father and have something of a normal life -- do you know what I would give for that? Get out of this madness while you still can!"
The thing is, Bruce may have an idea that the life Tim would be going back to wouldn't exactly be better for him.
Tim makes a point of saying in the letter that Bruce "knows" how people are... and thus Bruce probably has a pretty decent idea of just how controlling and emotionally manipulative Tim's dad is being at around this time. If he pushed Tim to ditch the tights and just go be with his father, at this particularly sensitive juncture...
Well, there are a lot of possibilities, some of the strongest ones not very good. The most likely is that Tim would spend the best years of his life caring for his invalid father (instead of merely assisting in his care as would be more sensible) and living his father's life for him, rather than his own life, steadily growing more bitter and hating himself for looking forward to the day when his father dies. Another likely possibility is that the resentment could grow and grow until Jack and Tim just had a big blowup, parted on bad terms, and finally leaves Tim with guilt and a feeling that he failed if they didn't manage to fix it before Jack died.
It's become popular in recent years to bring up how hard, how traumatic, how damaging a life connected to the Bat-Family is. We need to remember that very real, relatively common events between normal people can be just as painful and traumatic as any costumed villain's killing spree.