LACP only works if you have multiple data streams, so if you only test desktop > server, you will still have only 1GbE (SMB 2 only supports 1 stream, SMB 3 can work with multiple).
FreeNAS does not support SMB 3.0, so you can't take advantage of the multiple streams.
The only thing that can give you greater speeds is upgrading to 10GbE.