How can I limit the number of fingerprint attempts before fallback to other login type?
It could be nice to know how many "a few" is....


From Marshmallow Compatibility Definition Document (CDD) , quoted here


MUST rate limit attempts for at least 30 seconds after 5 false trials for fingerprint verification



  .... and whether this is an adaptive number that for example may take into account how recently it was correctly unlocked



CCD is silent on this so one could safely assume 5 attempts holds



  .... happy to force it to block fingerprint access after two failures, but I can't find this as a setting 


There doesn't appear to be any setting to increase or decrease number of attempts (google search)

LockScreen Tweakbox is said to increase the number of attempts to 20