Ntds.dit corrupted

I'd probably just power it off and seize roles on another functional DC

https://support.microsoft.com/en-us/help/255504/using-ntdsutil-exe-to-transfer-or-seize-fsmo-roles-to-a-domain-control

then do cleanup.

https://technet.microsoft.com/en-us/library/cc816907(v=ws.10).aspx

then build a new one.

If you have multiple DCs I'd use dcdiag / repadmin tools to verify health before starting. Then I'd stand up the new one, patch it fully, license it, join existing domain, add active directory domain services, promote it also making it a GC (recommended), transfer FSMO roles over (optional), transfer pdc emulator role (optional), use dcdiag / repadmin tools to verify health, when all is good you can decommission / demote old one.