@Hzza is the best person I know to help you on TMK keymap coding.
However, you can try again the tool as I managed to get TKG Toolkit working as well (was getting a never ending "waiting for bootloader" before) on a XP machine, with a little help of Kai himself. If you already installed the FLIP drivers on computer, then you should update the driver for bootloader by using
zadig which is in the tool folder. Then you can use reflash script to flash your keyboard.
1. Push the reset button and make sure the dfu bootloader appearing at "Devices and Printers".
2. Open zadig. Click "Options>List all devices" from the menu to enable the option.
3. Select "ATm32U4DFU" in the drop down list. ( Please be careful to ensure to select the dfu but not "GH60")
4. Select "WinUSB" as the driver. (Usually "WinUSB" is the default option)
5. Click "Install" button and wait for the installation finishing.
btw, I followed this tutorial:
https://imgur.com/a/rfezG