There are 6 BF's in act 2
If you need help finding the keys:
(SPOILER ALERT)
BF key lvl 4: in a secret room in
the lich cave (nr 10) {for the cave take exit 5 out of the mushroom forest}
BF key lvl 6: in the
treasure cave (nr 2) {for the treasure cave take exit 12 out of
the dead forest -> you'll need to toss one of your teleporter stones over the lava to be able to reach it}