3 quirky issues with High Sierra on a Dell Optiplex 9020

MacOS high sierra runs surprisingly well on my Dell 9020 Optiplex (i7-4790 3.6GHz, BIOS A21, 16GB ram, onboard graphics). But 3 quirky things need tending to. Any suggestions on any of these would be much appreciated. 1. A cold boot from clover rarely works (crashes, looks like a kernal panic, then returns to clover screen) But if I boot to the recovery drive first, then choose reboot from the apple menu back to clover, then boot the HD, all is fine. I can't explain why. 2. Ethernet drops its connection for a few seconds every 3 or 4 minutes. Annoying. 3. Although I am using an Apple aluminum keyboard, the volume and brightness keys do not work. I do see the white speaker or 'sun' icons in the centre of the screen, and the meter rolls up and down, but it has no effect on screen brightness or volume.

Thanks!