The gate designation doesn't really affect your airplane, it's used by the AI, and by FSX to have the parking populated by its own ground vehicles.
Since we have our own custom ground vehicles, and the default ones are very fps heavy, the parking are flagged as Ramp, so default ground vehicles will not appear.
Since the parking stands have AI airline codes and, since most users have addon AI traffic package anyway, the AI will still park correctly, without to rely on the parking designation.
So, both issues are not a problem.
About the "concrete barrier", that's just because, out of the 200+ parkings available at JFK, you chose the only ones that are actually closed for renovations, that's why there's a concrete barrier so, you are of course free to choose from all the remaining ones. There are plenty of heavy parkings available, the name doesn't really matter, what matters is the actual parking radius, and they are set correctly.
Just pay attention that, the actual numbering standard used is different from real life, because Flight sim numbering can't handle situation like at JFK with its naming convention (like having a terminal 5, Parkings from A1 to Axx and B1 to Bxx, for example ) so, you can use the ParkMe menu to see how the AFCAD naming is tied to the real world naming.
