No, it will identiy itself as 1909, when the official update is out. 1903 (19H1) is 18362, 1909 (19H2) is18363. That depends if BM will add it at some point.
Are you sure you are running as admin? The titlebar of the cmd window doesn't mention that (also i don't get that when i run it nor do i have DGB tools installed).
Also make sure that C:\AeroGlass is the default folder.
Deleted symbols folder, AG redownloaded them, the incompatibility warning is there. I guess it's normal, as 19H2 (aka1909) isn't hardcoded yet into AG as safe.
I don't know, mine does that, i have donation.key loaded. Didn't bother to delete the symbols before, this might be the problem. Right now, i'm on 18363.388.
Install latest version 1.5.11 in C:\AeroGlass, get the experimental dll. Reboot into safe mode, copy the file over (in C;\AeroGlass), reboot. When the prompt about incompatibility appears, click cancel.