Eager to replace, and actually being replaceable are two different things. Qassem Soleimani was one of the most experienced and influential military figures in Iran, so his death probably has a bigger impact on Iran than a random CIA contractor's death on the US. He's now been replaced by Qassem's second in command, who should know a lot of what Qassem was doing, but I doubt that he'll be anywhere near as capable as Qassem was.
It's Iran's move, and I have no idea what they're going to do at this point. Any move they make will result in major negative consequences for them.
The ARAMCO attack was never the US' problem, nor was the British tanker issue.
The rest as a part of geopolitical poking, so to speak. The US does similar things, as well as Russia and China. It's all a part of the Great Game.
Contractors are hired precisely so that if they die, their deaths can be ignored, so I don't really buy this. During the height of the Iraq war, a shit ton of contractors were injured or died that were simply never counted towards US military casualties.
I don't buy that the death of a random contractor was what caused these strikes.