Yes, it's a single municipality, my kids go to school there. Tel Aviv grew to be bigger than Jaffa we have huge towers here and Jaffa is an ancient city so you can't build up there.
The benefit of being a part of Tel Aviv means it has the same municipal services and advantages of being a part of the richest municipality in Israel.
You wrote "I live next to Jaffa and it is 100% an Arab city. Not "depopulated"" The wiki states it is only 37% Arab, and was depopulated, via expulsion. I guess you're trying to stretch the fact that the expulsion was not permanently 100% effective into alleging it never happened at all.
I highly doubt the 37% number though. I'm guessing it includes new construction on the outskirts as Arabic is the main language around in the street and in most shops. Looking at the Hebrew page there are more than 46,400 Arabs living in Tel-Aviv/Jaffa compared to 414,200 Jews most of whom live in the Tel Aviv region. Some Jews live in Jaffa but it's still very much an Arab city.
After the 1948 Palestine War, most of its Arab population fled or were expelled, and the city became part of then newly established state of Israel, and was unified into a single municipality with Tel Aviv in 1950. Today, Jaffa is one of Israel's mixed cities, with approximately 37% of the city being Arab. - https://en.wikipedia.org/wiki/Jaffa