Of course, the unit stays on whether with the key on or not. I can turn it off when not in the vehicle, but I am concerned about the battery, and bypassing the inline fuse, too.
You are right to be concerned. To have the unit stay on full-time (like a VW), you've got the +12v switched input connected to a +12 'hot at all times' wire. If you had both wires hooked up to a +12v switched, then the radio would turn off at key out / door open (RAP, or retained accessory power), which would drain the battery less, but you'd lose the clock / radio presets (no power for the 'keep alive' memory, so it's volatile).
No back-up camera and no amp in use.
'No amp in use' -- does that mean you didn't install an outboard amp, or that there's no (Bose) factory amp installed?
If there's a Bose amp installed, you'll need what Metra Electronics called a GMOS-04 (but I think is now known as AXGM-04, as Metra revised their product numbers). This is for factory systems with a (bose) amp where you want to retain the amp capability.
If you've got just the base radio, the GMOS-01 (or AXGM-01) should give you what you need.
Both include the chime box so you retain the factory chimes (they're built into the radio), and the harnesses make everything plug and play -- no wire cutting needed.
I've used both the GMOS-01 and -04 kits. My Sierra came with Bose, but since I wanted to run aftermarket speakers and bypass the Bose amp, I used a GMOS-01 there, and had no problems. Wired the Pioneer stereo speaker leads to the aftermarket speaks in the front doors (using adapters), and I was in business. (btw, I bypassed the Bose amp because they 'wear out' (break)).
I'm the oddball who likes Metra / Axxess (same company). I dislike Scosche because they have a reputation for being DOA or breaking. PAC, I can't rate, as I haven't used their stuff, but reviewing features of both, I picked Metra and have had good results.
If you have the steering wheel buttons, and want to retain them, get the AXSWC box. But I personally wouldn't bother... it's listed at $111, and the radio buttons are on the RH side of the steering wheel. Why pay that money to save six inches of reach? To be fair, you can remap the buttons with this device, so that the climate buttons on the LH side become radio buttons, but I still wouldn't bother, myself.
Note that Metra is listing a MSRP on the GMOS kits at about $179, which is pretty spendy (there's a good chance your Dual didn't cost as much).
For potentially cheaper prices, you can look on Amazon or eBay. Amazon often has 'returned' merchandise they'll sell cheaper than the 'new' stuff; I got two of the SWC boxes for $40-50 each, as an example.
Metra's site is at:
metraonline.com
They have a vehicle lookup engine, but more than one product can work with your vehicle, so it can be a little tricky to narrow down the choices.
Note: I don't work for Metra; just passing on what works for me. YMMV.
