Thanks for the reply.
For your point 1, I did look to make a firmware backup first, but my research said that it was impossible to take a backup of the BBSHD firmware, so I just had to risk it for a chocolate biscuit. There's not much I can do if there's no tool that works, sadly.
For 2, many...
I bought a BBSHD. While I could never get any version of the programming software to recognise my bike in Windows, the Speeed Android app did, and showed that my bike was limited to 25A. Trying to set anything above 25A gave a "current limit out of range" when flashing.
I found a firmware file...