This adds the "-C" for compression which helps with some things. I also had to use the "pi" account for some reason, probably to do with all my mucking around.
Just a note that using the native X protocol over the network can sometimes have very poor performance if the connection starts to have higher latencies. This is because the protocol is very laggy and a lot of things have to wait until the screen redraws complete.
If you're having problems with VNC, has anyone tried xrdp ?
XRDP is slightly different, in that it doesn't actually mirror the native desktop, but uses the MS Windows RDP protocol to run a new remote session on the Pi, but it might work better - so if multiple people were to connect they would each have a different desktop, although that isn't probably a good use case here, it still works with a single user.