I have also bricked a300 during crossflash and probably burned flash chip when trying to use flash clips with ch341a programmer. Same sympthons as yours.
The best method is to use soldering iron. Program blank flash with ch341a and find someone who can use soldering iron.
Also FWSQ is OK, i...
Upgrade from 3.60U to 3.70E went fine.
But you can't save any settings within bios, if you do so you'll get soft brick and cmos reset is needed (by unplugging cmos battery from motherboard)