Transferting large SQL Databases to Azure (>300MB)
You should use the Azure migration wizard instead of using SSMS create script.

How to: Use the SQL Azure Migration Wizard

Behind the scenes it uses bcp to transfer your data to Azure.

For the future, SSMS is not meant to handle large .sql files. Even a 1 or 2 MB file will crash SSMS. Instead you should use command line tools like sqlcmd or bcp - depending on your needs.