I got several reports that flash chip in T100 is designed to work at maximum 2V VCC. So either I was lucky or motherboard has good overvoltage protection. Exact chip used in mine T100 (I've checked today) is Winbond W25Q64FWIG (datasheet) which is not supposed to get more than 2V. However it survived flashing twice :)

Also, after the sucessfull resurrection I found a .docx file which seems to be a service center document- http://docslide.nl/documents/t100ta-fw-update.html
Document has embedded archives, one of them contains an old (2xx) experimental/debugging UEFI which is a full 8MB file suitable for debricking (bonus- you get service software for all sensors onboard).