1. Constraining the first stage to return over land would massively impact payload. This would be even worse than a Falcon 9 RTLS, because at least with that it can do a boostback, so the 2nd stage is still put on a relatively flat trajectory, just with earlier stage separation.

2. SpaceX tried using steerable parachutes for fairing recovery. Turns out, accurate enough to hit a small clearing for air-delivering supplies still has enough error that if you want to land it on some soft target, that target has to be very large. Larger than you think. The accuracy of GPS isn't the problem; parachutes are difficult to control with only a few degrees of freedom in control and are at the mercy of the wind.

3. A "target of crushable cardboard" absolutely wouldn't work. Since Electron's first stage is so light, I could believe some sort of large net, elevated above the ground could work. Probably cable-supported, with some sort of buffer on the cables to bring the net to a stop after the rocket lands on it. But that would be big and expensive.

4. A few hours of helicopter time is actually pretty cheap, especially compared to the alternatives. And catching things with a helicopter may not be common, but it is a proven technique with plenty of history behind it. And there's no shortage of very, very capable helicopter pilots able to accomplish such a feat.

The rocket is hundreds of kilometers away from land at that moment.

probably due to the horizontal distance it would have to traverse to get back to land (and uncontrollable factors that would limit that, e.g. wind magnitude and direction during launch). your sources don't give an overview of how far those parachutes can glide, but it feels like they are deployed relatively close to their intended touchdown point.

The delicate rockets engines would likely be damaged