That 35 Km was the area of total destruction, the effective destruction would have been larger. Even a 50-60 mega-ton bomb is absurdly powerful. 300 mega-tons are, in my opinion, overkill in the completely absurd range.
Not in elite. Remember elite is universe where hole star systems are in scale comparable to small towns. In elite you don't fight over single cities or even planets. 300 mega ton sound small weapon to be honest in elite scale to even be effective: In scale of elite destruction of planet with 7 billion people is nothing on grand picture. Wiping cities with 300 mega ton bombs seem like slow process in bubble scale warfare, like Americans bombing terrorists with firecrackers.