Feanor Self-Important?

[Maédhros]

I'll assume that your memory is still foggy on this subject, but does anyone else know if Fëanor retained his firstborn status in later versions?

I'm not sure what do you mean. In some of the earliest versions, Fëanor was not the first but second son of Finwë. He was at first the son of Bruithwir.
In the later versions, he is the first son of Finwë and Míriel and he is born in Valinor.