Based on your photo, my estimate gross score B&C for your deer is:
148 points.
Due to slight asymmetry they would knock off a few for the larger G4s on the right (of note his G2s and G3s are similar in size and are just really big!). Otherwise, your estimate and mine are almost dead on. I can tell this deer has great mass by the way your son is holding the antler on the left, his finger is almost wrapped around it and it shows the true mass of this deer. Really unbelievable deer, considering he is barely outside of the B&C record book (needs 160).
I would get it scored officially, there is a chance it could break into the 150s due to the insane mass. Again though, it will be docked a few for the asymmetry, and may push it back into the high 140s. Please keep us updated if you get a score on the brute. IMO, this is still a trophy, at least I dream of a deer like this, and he achieved it at his age already!