For me to know what switching to describe, let me know your model, I'm assuming this is one of those using more than just 1 volume and tone and a 3-way switch here (obviously).
Typically a Jaguar is wired this way
- Bass Side Control Plate, when active (Rhythm circuit mode) only the neck pickup is active and all other controls except this plate on the guitar are bypassed. It typically sounds darker than normal, sort of like Jazz guitar, fitting as it was lifted from the Jazzmaster.
-- Top Switch = RhythmLead Selector Switch, towards your head is Rhythm, Towards the Floor is Lead
-- Rhythm Volume
-- Rhythm Tone
- Treble Side Control Plate (Football Shaped some people call it), had 3 switches, these + the panel with the 2 knobs and output jack are active when the RhythmLead switch is in Lead Mode (toward the floor),
-- Top Switch = Neck Pickup On/Off - this is usually up (toward your head) to be on
-- Middle Switch = Briage PIckup On/Off - Same as the above, but for the bridge pickup
-- Bottom Switch = Strangle Switch aka High Pass Filter that cuts the lows out making the sound thinner like a "strangled voice" hence the name
- Control plate below bridge on the treble side with 2 knobs and output jack
-- Lead Volume
-- Lead Tone
-- Output Jack
The whole idea is that you can preset the two circuits for a setting and just flip the switch to change from rhythm to lead, though almost nobody uses the rhythm circuit, and those of us who do don't use it for rhythm, I actually use it for more of a Brian May sustained sort of thing myself with high gain TBH.
Can't see any of your pictures BTW. - the crack by the bridge may just be finish deep, on a Jaguar I don't think it's anything of consequence unless the crack travels all the way into a cavity somewhere. That's the easiest way to tell if it's a crack. Finish does crack sometimes.
As for buzzing frets, it's fine if it does not go through the amplifier (I set my guitars up that way), but if it really bothers you, and what you describe with buzzing on random strings and frets, I can only think it's the frets are not perfectly level, the only way to tell is to take it to a tech, or if you are comfortable doing this, you can use a flat sanding block with some high grit sandpaper after you mask off the fingerboard and mark the frets with magic marker, the remaining magic marker will reveal all the low spots. For best results might want to get some kind of metal bar or something else certifiable as 100% straight or designed for the radius of your fingerboard.
