1) GH off airhits allows 5B, somewhat
Possible in CS2. FC only
2) DS > TK GH
Again, also possible in CS2, but stupid hard now due to the Dead Spike launch change
3) Looks like that Tsuika loops are not worth anymore for BK Heat building, DS 5D's are quicker and give moderate heat.
No. This should only be used when you used 3C rapid cancel because you have less time. Hell's Fang loops still give more heat. (Btw, 50 meter BK combos still exist in CSX)