The long ground wire you are running for the 200.4 may well be the issue. I usually ground the amp as close to the amp as possible. You could also look at the quality of the grounding point. Not sure if you scraped the paint away to give a good connection, but the layers of paint might not...
Cactus Gray case with red emergency button. Really easy to swap the guts of my tundra key into his case, hoping this one is the same. I will post pics once I get it.
I am giving this one a try:
https://www.ajtdesign-llc.com/online-store/Injection-Fob-IF019-2017-Ford-Smart-CACTUS-GRAY-PREORDER-p468720686
I used a lot of the AJT products for my Tundra and they are great.
5 Icon Rebounds for sale. 17x8.5, 0 offset. I used them for less than 1000 miles and then went with a different option. Asking $1000 for the set, but open to offers.
Yes, I tried moving the amp around to every possible place in the wheel well but I could not get it to fit mounted vertically. The issue I had was the shelf that runs along the trim panel and ends at the 12V plug and cargo light. I couldn't get the amp to fit around that.
No idea what the factory head unit puts out in terms of RMS. There is probably some way to measure, but not something I ever had curiosity about. Fair to say factory power is low.
However, I am pleased with the full range signal you can grab from the front channels. I have found it has...
That is a great picture posted by @pjmezz13. It clearly shows the full range signal to the fronts and the attenuated signal to the rears.
Here is a picture that shows the electrical output of the head unit with some EQ adjustments (gray line) and then the audio output of the complete system...
I went with the tweeter/woofer combo of a 2-way setup to get the complete sound I want. I'm not surprised that dropping in a set of good speakers (your Morels) and leaving everything else the same didn't have much of an improvement. I suspect that the factory head unit doesn't have enough...
That is one thing I forgot to mention: the storage cubby! I had to remove the whole thing to get my amp to fit. If anyone has to do the same, I used a utility knife to cut the plastic welds on the inside. Not too hard and only cut myself once.
The removable sub box with quick disconnects is a good idea. Once I put the slim box in I was really surprised at how little volume it took away. It's a 12" sub with the following dimensions: 27.5"W x 6.125"H x 14.625"D. You can get even smaller with a 8" or 10" in a sealed box.
The amp...
I am sure it would work. My concerns would be using an aluminum box sub on the tailgate might be a source of unwanted vibration and rattles. I may be completely wrong, but a box with more mass and different material might help to dampen vibration. Maybe something like this...
My Build:
https://www.bronco6g.com/forum/threads/complete-stereo-install-amp-dsp-speakers-and-sub-lots-of-pictures.43856/
Only thing left from the factory system is the head unit.
There are lots of good threads in this section about different ways to approach this. From the questions you are asking, you might want to go with a plug and play style harness with all of the connections already complete. Then you can just plug in the matching connectors, power and ground...