Form 8915b is not ready, but I am no longer getting the error that the form has not been finalized. Should I file or do I still need to wait for form 8915b to be ready?

You can file an extension that gives you until Oct 15 to file, but sill pay any tax due but April 17.

https://ttlc.intuit.com/questions/1900551-can-irs-extensions-be-e-filed

The "Relief for hurricane distributions" Requires forms 8915A/B that now has a 3/22/18 target date.

The IRS only released the paper/pdf for the new 2017 8915A and 8915B forms on 3/6/18 and the electronic schema specification are usually released by the IRS about 2 weeks after the pdf version. E-file providers must comply with the IRS schema rules to e-file.

After the IRS provides the electronic "schema" for the form, both the IRS and e-file providers must apply those new schemas to their software and conduct compatibility tests. Only after the IRS approves the test results can the forms be released in an update.