Great questions. This happens to most everyone who does prototyping. The loose terminals are a function of the quality of the breadboard. Also the wires used, if too thick can cause them to get out of shape.

I typically use wires that have the ends already attached. Here's an example from Amazon; Even with these, I've had situations where the breadboard itself had holes that were intermittent. There may be a brand of breadboard that doesn't have this problem, but I don't know what it is. Maybe someone else can offer some suggestions.

As far as making it permanent, Using a prototype board, wires and solder is the best way to get a more permanent build. It takes some practice, but like most things, the more you do it the easier it gets. Here's a picture of what I'm referring to. This socket will hold the level converter needed to control the LED string.

For anybody reading this thread, I also found that the standard breadboard was flaky due to lack of good connections.  Symptoms were that the Pi would reboot frequently (like right after the splash screen), or that when the light sensor would go high or low, it would restart.  I bought cheap solderable breadboards and the act of soldering meant there were no more flaky connections.

There's a kit with 5 breadboards for $12 ( https://www.amazon.com/Gikfun-Solder-able-Breadboard-Plated-Arduino/dp/B071R3BFNL ), but ultimately I used the Adafruit breadboard with the Raspberry Pi header built in and recommend that.  It's $8, but much easier to connect your Pi to.

Thanks for the info. We've had a number of questions regarding flaky operation of the LED's and I suspect most, if not all are due to the breadboard connections. - Mark