Fëanor's Death, Convenient?

[the phantom]

I don't think that it was grief for his father's death and Morgoth's lies that drove Fëanor to do what he did in Aman.

Really? I thought that was exactly what drove Feanor to his actions. Manwe refers to Feanor being marred by Melkor, which means without those lies Feanor would've been different.

I'm sure that he had wished for his father's death more than once in his life

You are assuming a lot, and that particular assumption holds no water. The Silmarillion says that Feanor loved his father more than any son has ever loved his father.

Fingolfin was the strongest of the Noldor. If he couldn't kill Morgoth, then how do you expect Fëanor to?

Just because Fingolfin was the strongest doesn't mean that he could beat Feanor in a fight. Though Fingolfin was a bit stronger, Feanor was likely more agile and had more perfect coordination (the coordination is for sure, since he was such a great craftsman), and any fighting or weapons expert would tell you that that would give Feanor the greater advantage in a sword fight. Now, I'm not saying he would definitely win, but I'm saying that it's certainly possible. Remember, Feanor fought all by himself against a few balrogs for some time before he was finally struck down.