Even if the judge rules against Altmire, he can appeal to federal court, because residency requirements for petition circulators are unconstitutional. They've been struck down in a bunch of states.
Yes, but signatories to a petition must live in the district, so it may not be unconstitutional for the circulator of that petition to also be a resident. I'm curious if there's a federal case on this question.
Morrill v Weaver is almost exactly on target, other than it applied to a minor party. In Pennsylvania, minor parties do not qualify directly, but rather their nominated candidates petition to get on the general election ballot in a way parallel to independent candidates. The party qualifies based on the success of the party candidates (it might just be governor).
In the case of Morrill v Weaver, the Green Party was trying to get on the ballot, and the gubernatorial was gathering signatures for his run, but couldn't witness signatures for district candidates unless they happened to be in his county.
In collecting signatures to get on a primary ballot it is somewhat different in that potential candidates are competitors. It makes sense to require signatures to be collected by someone who is affiliated with the party. Otherwise, an opposition party could run a primary candidate. Whether someone who resides in another district could be considered an outsider, is another question.
In Pennsylvania, they determined that the person who collected the signatures lived with her parents (in the district) even though she had rented an apartment.