You should leave the phone until you cannot find the hotspot anymore. Maybe the wifi module blocks the phone somehow, it is a long shot. Then charge it and see if anything changes
Ok, again I am impulsive, no sign of life you said other than wifi hotspot. I am stuck here. If you tried everything and there is no output I am really clueless
Please try using lg pc suite or lg mobile support tool in order to perform the update.
Just google pc suite and install it. If you have the same result, repeat the steps using lg mobile support tool.
Please post the result (whatever that is) here. We will sort this out