We use a Firebird server for our software project and we had a custom build of NHibernate to enable full sequence support for our generated Ids. Now we updated to NHibernate 3.2 and Fluent 1.3, where there was the old FirebirdDialect again.
I decided to run your unit tests from your git repository with this small modification. There were 755 failed tests before the change and 743 after - still quite a lot, I think I ran the unit tests using ReSharper unit test runner, because I was not able to build all test assemblies (my Visual Studio does not have support for Visual Basic installed). The test environment was a Firebird 2.5.1 server, a database with 16K page size and no charset, NHibernate.Driver.FirebirdClientDriver and the NHibernate project's default .NET version.
I attached a patch and the output from the test runner. I am fairly new to this issue tracker and git, so I hope, this was the right way.