3" is fine, but your cooktop manufacturer, not your dad, is the boss here. They have specific clearances from combustable walls. Look it up, please.

In addition to clearances mentioned above, keep your aisle widths in consideration, and not cabinet to cabinet but counter to counter (since counters have an overhang.)

If you decide the bump isn't quite enough, you can cheat a little by increasing the overhang of the counter edge.

Your hood will need to be bumped out by the same amount of space. Install a 2x4 behind the hood, wrap the edges in stainless steel (can be cut at HD, Lowes, etc.) in order to bump out the hood.

Why are you just bumping out the cooktop? Many people on this forum have done deeper counters, i.e. 27" deep instead of the 24" deep for the entire counter run (they also bump out the uppers by 3" to match). If you bump out only the cooktop, are you creating two corners sticking out that you will often be hitting with your hip?

Wow! Thank you everyone for your responses!

I'm not doing the entire cabinet run because I'm using the cooktop as a focal point and am pulling it forward just a little to really set it off.

The cooktop installation guide indicates that either location is fine. I will have enough clearance. The bumpout is purely aesthetic. I'm clumsy but rarely bumped my hips on counters like this at other homes I've lived in.

As for aisle width, that's another area I was really concerned about. I set up dummy cabinets at the counter depth to help understand the space before I ordered my cabinets.

Thank you all for responding I really appreciate your thoughts! I love this forum and I've rarely posted but I check here all the time!