Did a little work this weekend.
Tried the black plastic garbage bag on the back window to see if that helped with the tint removal. To my surprise, it actually loosened up the remaining tint enough for me to peel/scrape what was left of it off. It didn't go as smoothly as the videos I saw, but it at least loosened it up enough for me to get it all off. I used the bag with regular 409 cleaner. One item off the list, now I can get it scheduled for new tint. I'll be going 20% all around.
Also messed with the radio some. I re-ran the amp ground to the rear seatbelt bolt. From my limited garage testing, it seems to have helped, although it didn't eliminate it completely. I won't know until I drive it for sure as to how much it helped. I was going to try and ground the RCA outputs to the HU chassis, but quickly got frustrated with that and gave up on it. I have some PAC ground-loop isolators on the way this week. I'll get those installed and hopefully that will take care of the rest of that issue. Driving my truck this morning ('16 F-150 Super Crew) I realized how much better my audio system is in it compared to the car. Granted, I've got much better equipment in it but the difference is staggering. I'm running JL C2 components up front - they make a ton of difference compared to the NVX budget components in the car. For the difference in price, I should have just went with those again. But, budget.