No, you don’t have to use the ceiling as the fully indexed rate. The fully indexed rate is going to be your index at consummation plus your margin.
Check out the commentary to 43(b)(3) – it gives various examples that might be helpful.
And yes, you need to calculate the payment for simultaneous loans (other covered loans or HELOCs secured by the same dwelling and made to the same borrower at or before consummation) in accordance with 1026.43(c)(6). And I’m not aware of any specific calculation for credit card debt under the general ATR other than under c(7).