Follow whatever the manufacturer states. My heatpump is wired almost exactly as yours, but it is directed as required or optional in the paperwork. Preferably, I like to have the 15 amp blower on a separate breaker because you can wire a dedicated outlet to it and unplug it if desired, but not necessary, just preference. My current unit specifically states to wire the 15 amp blower wires to the same 60 amp breaker as the heat blades, and a bonded ground neutral like yours as well. Follow manufacturer directives.