1. LB residents don't want that, and limit of 2 has worked until now. Height restrictions are nearly universal in the US and this is not a California/Long Beach specific problem. Sure you can argue there the balance is too lopsided and limit of 2 is too restrictive for industry. I tend to believe a port town is an industrial town. If you live there, you should expect to see the industrial side. I grew up in Houston and would never live near the port/oil refinery areas because of that eyesore (completely subjective personal opinion). Unless maybe my profession was tied to it, at which point it probably doesn't bother me.
2. What if it was stacked up to LIMIT and a wave of containers come again? The point is to reserve a buffer. I'm rather agnostic on the numbers use variables if you like; Normal limit X, buffer size Y, X+Y is what you can get a temporary permit for, Z is technical limit and this math is a test X+Y <= Z