Gotta remember that these costumes are replicas of a costume that was literally designed to survive filming, and ONLY that. Trooping conditions are not conducive to a long-prop life for the nature of Jango/Boba costumes. There's quite literally hundreds of things that can go wrong simply by walking, let alone standing. That being said, you need to evaluate just how your personal suit is built. It does take a degree of experience, but the great thing about the internet, and this site, is that you can see the many possible ways of how things are assembled/put together.
As Mullreel said, the rangefinder should be a simple fix, but I'm not sure what kind of helmet you have or more details of what's going on.
For your leather belt, which belt and what is coming apart?
And for your jetpack, you need to take a day or two to really sit down, figure out what about your strapping system is making things difficult. Perhaps you need to get a new jetpack harness. I know I developed my girlfriend's system such that the Jetpack harness straps are set precisely where they need to be when ever she puts it on. The straps/buckles for the jetpack itself is fixed, so it's completely dependent on the jetpack harness straps to stay in one spot. Sometimes you have to make things simplistic since, as you said, you have to rely on a handler to help you get dressed. My snowtrooper chest/backpack strapping is stupid-proof, even if a person manages to put my pack on upside down, it won't work right. I did this intentionally and sure enough, I have almost no issues with handlers helping me get dressed, without ever even seeing a snowtrooper in person before.
So, take your time man. Just sit down and figure it out. Prop/costume building is all really about problem solving, at least that's how I see it. If you let it get in your head then you're not going to progress forward positively.
