In 2017 I made a tax year 2016 $5500 nondeductible traditional IRA contribution. Later in 2017 I converted that contribution to a Roth IRA. In December 2017 I recharacterization the appreciated amount back to a Traditional IRA in my Fidelity account that didn't post/complete until January 2018.
You should carefully read page 4 of the instructions for Form 8606 ( https://www.irs.gov/pub/irs-prior/i8606--2017.pdf ) which tells in example (2) how to go about this. From my reading, you did everything right in 2017 except for attaching the statement to your return. If, as I assume, your 2016 year 8606 basis was augmented with the original nondeductible contribution, then the basis stays the same modulo any new tax year 2017 contributions. For 2018 you simply add the basis of any new nondeductible contributions.
As to your 2018 return, I would report the 1099-R in box 4a and not include it in box 4b of your 2018 Form 1040. I would also attach a statement to your 2018 return explaining the above transactions.