Ok I think I'm clear now. The only thing I am not sure of is why the $5500 shows up on the turbotax user interface for 2018, but I checked my 2018 return and there is no 8880, and the line on schedule 3 "retirement savings contribution credit. attach form 8880" is blank. All lines that reference "IRA" are blank. The only place I see anything about IRA is a short page called "Additional information from your 2018 Federal Tax Return" where there is a recharacterization explanation I wrote for the $1000 that was put into Betterment in 2018. So it seems fine.
Thanks for your help clarifying all this!!
