Thank you for reaching Microsoft Q&A Forum!
I understand that you are trying to create a synchronization service account, and you have received the error message. based on the information you provide it seems there are multiple errors are shown.
May I know how you have created the service account? in general you can only set the service account on first installation. It isn't supported to change the service account after the installation has been completed. If you need to change the service account password, this is supported, and instructions can be found here.
For more information please read the ADSync service account.
Hope this helps. Do let us know if you any further queries by responding in the comments section.
Thanks,
Akhilesh.
If this answers your query, do click Accept Answer
and Yes
for was this answer helpful. And, if you have any further query do let us know.