Please correct me if I am wrong in my thinking, but the way that I am seeing this there are 2 incidents occurring in 1 action, each incident needs to be addressed separately.
Incident 1: F1 obstructs B/R.
Award B/R 1st at end of playing action, unless they acquire it themselves.
Incident 2: Ball entering DBT.
Award B/R 2-bases from time of pitch.