Database migration program, that can analyze source and target db, and tell diff
There are multiples alternatives out there. I would recommend these two:

Idera comparison Toolset and the Red Gate SQL Compare &amp; Red Gata Data Compare. All of them offer full funcionality during the trial period so you can take a look and decide which one is better for you. They work in a similar way: you select source and target databases, compare and generate deployment script with the differences.
For database diagram you can also use the Red Gate Dependency tracker. 

I use Redgate ones everyday and used Idera in the past so let me know if you have any issue.