Just add the other five DeviceProperties, as shown in the screenshot below. You might not need an SSDT if the framebuffer patches work with your AMD system.
View attachment 9706
I don't think you need the -radcodec boot argument either, but that is another matter.
The device path for your discrete GPU is (_SB.PCI0.GPP0.SWUS.SWDS.GFX0) according to the gfxutil screenshot.
So I googled about this Henbury issue, and my GPU doesn't seem to exhibit issues with high temps. as I type this my GPU is idling at around 44 C and occasionally drops down to 42C.
I ran the Heaven benchmark and the GPU temps spiked up to 63 C, but that is hardly of concern. I will add these Strings to my config.plist but I don't think it will help.