Great job on the wiring.
On the switch, the wiper switch is on metal plate, while that plate is connected to the bezel (plastic part), that plate serves as a ground as it is connected to the dash frame at some point (I would have to go and look at it again to tell you exactly where). That said, in my Cuda, I ran an independent ground wire from the plate to a ground with a disconnect so that I could remove the switch panel and replace it without issue. The factory used some pretty sketchy techniques to ground everything relying on a variety of screws and 2 bolts, but the success was dependent not having paint or other coatings between the surfaces and thread to thread contact.
To this end, you can make life a lot easier for you by doing the following;
1. run a ground from the alternator body to the block
2. run a large ground cable from the engine block to the K frame
4. run a ground from the dash frame to the firewall
5. run a ground from the firewall to the engine (there should already be one there, but check it)