The DBCC statements you issued will not reduce the size of the buffer pool (the specific area of SQL Server memory that is used to store data pages).
DBCC freeproccache: Releases any cached query execution plans from memory.
DBCC FREESESSIONCACHE: Flushes the distributed query connection cache used by distributed queries against an instance of Microsoft SQL Server.
To answer your second question, the ‘sql server memory = 32766 MB’ is a SQL Server setting that states SQL Server is permitted to use up to 32GB of memory if it requires to do so.
Inspecting the DMV SYS.DM_OS_SYS_INFO shows that your server has:
physical_memory_in_bytes = 17177374720 bytes = 15.9976768 GB
bpool_committed = 1728512 = the number of currently committed pages in the buffer pool not their size.
To get the current size of the Buffer Pool, multiply the number of pages by 8(kb) so your current buffer pool is
1728512 X 8kb = 1.6484375 gigabytes
In order to get a detailed report of SQL Servers memory usage I like to use the DBCC statement:
Hope this helps.