Using etcher should solve your partition writing problems since it writes the entire image including partitions.
As @r043v try a different card reader, or even another physical computer. I personally use the SD reader built into my MacBook Pro, using a SD micro to SD adaptor.
Let etcher do it’s verification thing to make sure the image was done properly. Also make sure you eject the card properly when removing it.
Another thing. Try holding the power button for ages. Like 20 seconds. Also try holding the power button, then pushing the reset button. I don’t know if there is any official hard reset rescue me combo, but this would usually be it.
I’m not sure if it’s been assembled the whole time, but also try having the battery disconnected for a few minutes then trying again. Then try having it plugged into USB power for a while, then giving it a shot. I’m thinking re: battery calibration problems.
Occasionally I have had my unit power on to show the splash screen, then just go black. I attributed that to the fact that I have worn out my battery, ie leaving things to compile for days on end, and not having enough current to push through the boot process.
On the note of not enough current, check your cable leading from the battery to the mainboard. Really make sure it’s pushed in, and that the wires aren’t pushed out of the headers of anything. Also, make sure you’re using a dedicated USB micro charger, say a 5A one.