There is a slippery slope with the classification of what is a felony that will result in the lifetime ban, and that is something that is mentioned in dicta in the opinion and its concurrences. I will note for everyone though, that under Delaware law, if you are convicted of a violent misdemeanor, a domestic violence misdemeanor, or a drug misdemeanor, you are a person prohibited for 5 years from the date of conviction.
As for the Government's appeal rights, you are correct. Since this is an en banc opinion, the only appeal that the Government could take from this is upon writ of certiorari to the US Supreme Court.
Though this is a narrow decision of the court, it is a precedental decision and it is one that will certainly be a good guidepost for future 2A litigation in jurisdictions covered by the Third Circuit (i.e. DE, PA, and NJ).