Can an incumbent candidate use the Phrase "Re-Elect" to District 4, IF (due to re-districting) he was never elected to that Dist

He will probably get away with it unless your local Board of Elections adjudicates unfair campaign practices in a timely manner -- hopefully before the election. You should check into whether your local League of Women's Voters has a "Fair Campaign Practices Committee" before whom you might be able to lodge a complaint. These committees sometimes issue their findings in press releases that are in turn picked up by the local papers. Good luck.

It would certainly be better practice to use the phrase "keep" or "retain" rather than "re-elect" given the circumstance you describe. A consultation with a NC election lawyer could get you an answer on whether it's a technical violation. But, as Mr. Binder points out, the timeliness of any redress is likely to be rather later than you might hope.