It won't be inherently more secure, the same flaws will still exist, it will just be less visible to attackers, thus obscurity.
Hiding things has its value. Learn how to use all tools at your disposal, wisely.
One could argue all security is "through obscurity". The encryption key exists somewhere in the parameter space, which is open to everyone. You just don't know where it is.
It is more productive to think of the onion model of security. Any technique is just another layer in the onion. As long as you have a sufficient number of layers, and they're all good in different ways, you're probably fine.
Of course not, and frankly that's a gross mischaracterization of the parent's point. The problem is not that security through obscurity is the devil; the problem is that security through obscurity is not security, and is not useful when you need security.
> The encryption key exists somewhere in the parameter space
This misses the point of cryptography, which is that you (roughly) have to try each possible key separately. So, for example, the combination of a 64-bit security layer (or set of layers) with another 64-bit security layer is a 64-bit security layer, not a 128-bit security layer, which you should know if you know what "parameter space" means.
Anything that reduces the likelihood of success of any attack is security. Non-standard ports essentially remove you from the radar for a lot of dumb IP block scanners. That alone is worth the minimal effort involved.