About my GPS problem, I finally factory reset Android and it seems to have solved the problem. So hopefully it wasn't a hardware issue, but just some app that messed up settings, or maybe I did something wrong.
Moreover, I made it even better than before. I found an awesome app called "GPS Keeper", which keeps the GPS lock from going cold. That means, if you stop your navigation app and reopen it at a later time, after you drive for a while, there won't be any delays anymore. I am using the pro version, which allows it to run at boot time. That means, if I leave home and on my way I decide that I need some guidance, the nav app will instantly have my location, no more waiting for the GPS to find the fix.
Some other change that considerably improved my experience, was to add the GBoard app, for a proper keyboard app which is easier to type in (addresses for example, in the nav app).
I complained before about brightness, at night. I have finally found the brightness control option, it's hidden under "Camera/Video Settings" (for some reason). On top of that, I just realized that I can use the power icon on the top right corner to turn the screen off completely (not sure how I missed it until now

).
One thing that bugged me was the fact that the Bluetooth options were missing from the Android settings, so you can't connect other devices to it. I now learned that the reason for this is that the unit uses a custom Bluetooth module, to enable the device to act as a sound receiver from your phone. And I think I might be able to use an USB Bluetooth dongle to add the functionality one has on a regular phone/tablet.
A tip for those that are going to install the unit: sound proof the plastic around the unit (not sure how, tape, grease or whatever) because it can make a lot of annoying squeaky noise on less than perfect asphalt. Listening to music covers the noise, but without the music it bugs me enough to wanting to redo the install.
So, after three months of using the device, would I buy it again? Yes, I would.