Re: Tone Darkening
Depending on your age, "voicing" may be too difficult a concept to grasp. Your setup sounds fine. I'm not a big fan of Jupiter saxes, but you can definitely get a decent tone on your current reed/mouthpiece combo.
I'd recommend you work on breathing. Read some books/websites on proper breathing (I like the stuff out there for singers). Take a full relaxed breath, keep your throat open, corners (embouchure) in, and don't pinch the reed. But without doubt, breathing is the secret to a good tone.