trying to install a new stereo unit in 2007 Agile SS

Hi folks: I recently purchased a 2007 Agile S/S. It's great! But the old stereo in there only plays old CDs, not even MP3-formatted CDs. So I spoke to the good folks at Crutchfield and bought a new Kenwood head unit that is not too fancy, but plays MP3-formatted CDs, connects via Bluetooth to my phone and music player, and has an AUX-in input for my music player too. All good.
However, after 5 days of testing and tinkering around and 5 calls to Crutchfield, I am told that the only solution I have to wire this new head unit on is to have it connected on all the time (in which case I am told it will drain my battery in 6-8 hours, even if OFF); to connect it to a manual toggle switch (if I forget, the stereo will drain my battery); or (from a forum) to take the seat off and find the ignition-switched lead and connect the stereo to that.

Before I take the seat off, I wonder if others have had the same experience. I was told after the fourth call to find a switched fuse such as the windshield wipers and tap into that for the power to my stereo. I bought a tap fuse and found the fuse for the windshield wipers. I put it in, and am pretty sure that I got the direction correct. However, I am finding that every single fuse on my NCV3 Sprinter is constant -- all are at +12 V whether the ignition is on or off, or the door open or closed.

The stereo, when connected to the windshield wiper fuse, is ALWAYS on. Yet, the windshield wipers operate correctly -- they only operate when the ignition is on. The most recent Crutchfield tech (a supervisor this time) tells that I am seeing these confusing results because everything is data-driven in this Sprinter RV.

So my questions are:
1. Has anyone found a way to connect to an switched fuse in their Sprinter, and if so, which fuse(s) are switched? I would love to find a switched fuse that I can connect to that is either in the box beneath the drivers side seat or the fuse box that is near the hood release, near the drivers left foot.
2. If I install this head unit and turn the power on and off manually (eg I have to push a button on the stereo to turn it off), and it is in the OFF position, will it really drain my battery in 6-8 hours? If not, would this be advisable? I could put in a toggle switch but I still run the risk of forgetting.
3. Does it really make sense that the windshield wiper fuse is always on, yet the windshield wipers only work if the ignition is on? And that a tap from this fuse is ALWAYS ON? And that this is explained because "the Sprinter is data-driven"?

Thanks for any insight.

I believe it was in the Unity forum that a fellow was having issues with his coach batteries draining... turned out it WAS the replacement radio head unit. (What the H***'s a "head unit"??)

And YES, these things are all run by computer, so there's going to be some electrons zipping all over the place, all the time. Apparently even a replacement bulb with a resistance different than the original can create problems. Welcome to the 21st century. Like a lot of others, I'm still learning.

Good luck with your problem.