Nova destroys him. Mar-Vell had very good fighting skills and did good against guys like Thanos cause they were much slower than him and he could dodge everything they threw at him, etc. He was never that powerful, and it hasnt changed. And against someone not only far more powerful than him, but also faster than him, he's in big trouble.
Flow at presumably trillions of times the speed of light. Be said to be able to cripple the Phalanx. Break out of the Phalanx's control. Beat Annihilus once the Q-Bands were removed from him. Being stated more powerful than Quasar. Own Drax. Take everything the Thunderbolts could throw at him, and just be angry, not hurt at all. Destroy tons of Kree Sentries. I dont think i need to go on, and ive only hit the tip of the iceberg.
The only feats that mean anything you've said, were the trillions of times the speed of light, and the Kree Sentries.
But that trillions of times the speed of light, would have helped a bit when he was trying to catch She-Nova... IMO. Although, I like how you speculated on his speed.
The rest are meaningless. And if you want to use that Annihilus feat as evidence of power, then Mar-Vell beat Annihilus because he made him hit his light that flows behind him.
I've no doubt that Nova could turn out extremely powerful, but so far, he's shown to be overrated... by you, like many others.
Could he beat Mar-Vell? Maybe.
Is he far above Mar-Vell based on feats? No.
He's acutally going to be limited for a while cuz he's basically at 20 % power due to the virus, which is why i omitted it for the purpose of this thread.