|| If your Rabbi is Sephardic you can certainly follow his Minhagim and all. If you don't have a Rabbi, go out and get one."
Does that mean that even if you can ascertain your father's family's Minhag, you should opt to adopt your Rabbi's minhageem in lieu of your father's family's minhageem?
Reply: "if you can ascertain your father's family's Minhag"
This sounds like you did not grow up with these family Minhagim. Your Minhagim should certainly follow your Rabbi.
Actually, since your father was not observant, and I dont mean this in a demeaning way, you would be doing exactly what your father did...He didn't follow his father..and if you dont follow his you would be in keeping with your family's tradition.