If you haven't already done so, check the database-related sections of the System Requirements chapter of the ePO 4.5 install guide. In particular, things like nested triggers and collation can catch out the unwary
Otherwise there's no special requirements - it can make life easier if the SQL browser service is running, but it's not essential: it just means you'll have to manually enter the server information during the install.
The EPO 4.5 install didn't like any other DB name besides the default DB name when I installed it on our separate SQL 2005 backend, and it really wants Windows Authentication for the account access.
Sorry, I must be missing something... the ePO 4.5 install shouldn't ask for a DB name: instead it should create a DB with the naming convention of ePO4_<name_of_ePO_server>. What was the installer asking you for?
Re: SQL auth - it'll work quite happily with SQL authentication as well as Windows - the only thing that catches a lot of people out is that we require a minimum permission level for that account, so if you try and use a simple user account it will probably fail. Ideally is must be the sa account or an equivalent.