Best wax and way to wax front of faded fiberglass TT?

That picture shows, to me, the cap is not that bad. You could just try a marine wax and see if it meets your approval. There are various cleaners and deoxidisers sold. TSP or TSP substitutes are a good, inexpensive deoxidiser. The marine waxes will last the longest.

Edit: Looking at the picture again, it looks like the faded portion has a pattern. Did someone scrape up there with something coarse? It may be that you need to use some rubbing compound and a buffer to get that all even again.