For the 5B > 6A blah blah combo, it's either one of two things:
1. You're not doing j.C quickly enough. You can help your execution by doing what's called "advanced input," which basically is holding down the button. Doing so will repeat the attacks for 5 frames, making 1 or 2 frame links really easy.
2. The combo's invalid in the first place. I highly doubt this is it though, the proration's only at 19% (I think), meaning only a 5 frame tech loss. That's still not enough for the opponent to tech out of j.C.
As for BnBs, these will help you:
5B > 3C > 5D > dash 6A (replace 5D > dash 6A with 2B > 5C if the opponent is far away) > hjc j.C > j.D > jc j.C > BE > 6D > j.D > jc j.C > BE > dash 5D > 22C
Does about 4k.
6B > 2C > 6C > dash 5D > dash 6A > hjc j.C > jc j.C > BE > 6D > j.D > jc j.C > BE > dash 5D > 623D > 236C > 214D
I think this does around 3.8k, not too sure.
GH > (near max delay) GH followup > dash 5B > 5D > dash > jump j.B > j.C > jc j.C > BE > 6D > j.D > jc j.C > BE > dash 5D > 623D > 236C > 214D
3.8k again maybe.
All of these only work in the corner, unless you add a dash to your 6D (but it's kind of hard to execute). You can always replace everything after the first BE with 3C > 5D(1) > 214A > 214D for good oki, or 5D > 22C if 22C is available.