1. Sure, it certainly will. A less flashy way would be wrapping a red string and whispering, ''you are bound'' nine times, if a binding spell is what you are aiming for. If the poppet represents someone. If you want yourself bound to the poppet, as in, the poppet to represent you, a piece of hair or even your energy through a psi-ball is enough.
2. Yes, and yes, depending on your intent. You can heal like that, though there are definitely other means of doing so with a poppet. The needle is representative of action, the moving energy of the ritual. If you want to cause pain, you will use a needle imbued with some darker energy. Preferrably black or red.
Sometimes such ''direct'' magic can be effective, but if you wish to curse, you should opt for lesser methods, some mental(like inducing insomnia, nightmares, depression...) or circumstantial(bad bad bad luck, etc.) since there's a fairly strong chance of dirct physical pain not popping up.
3. Put your energy into it, and then cut the line, the one connecting you and it. In essence, the poppet looks like you, and has the same energy signature as you, so a sloppy magical attack, which is basically most wannabe dark wizards and wandering spirits, will be redirected at the poppet, which is now your decoy. Any alarms you have will go off, and let you prepare better defenses.
As for putting wards around the poppet to defend yourself, its possible for a more elaborate protection, but for all intents and purposes, that would be overcomplication, when you could just be casting all of this on yourself rather than a doll meant to symbolically act as yourself.