Update:
My $100 GC purchase in store at BB from 4/23 did the 1 SB pending that so many experienced.
4/30 shop ticket resulted in almost instant credit for the other 399 SB.
On 5/9 I got 500 SB credited for a targeted $5 Shop (had to spend at least $5 and earn at least 25 shop SB by the end of April). I did not submit a ticket, and worried this wouldn't go through since the 399 were "good faith" SB rather than traditional shop credits, and this was my only SB purchase during the timeframe.
Today, 5/10, I submitted a ticket for the 750 bonus SB, and they were credited to my account within a few hours.
So, total of 1650 SB for a $100 GC. I'm a very happy camper!
Thanks so much to all of you who shared your tips for phrasing credit requests, and gave me hope it would go through.