How do we connect a front end application to the application deployed on Azure Blockchain workbench?

As a (temporary) alternative to the (IMO incomplete) REST api, you might consider using an ORM such as EF or Dapper (read only!) to query the SQL tables deployed by ABW. The structure is fairly easy to understand, and there are foreign keys between the tables which will define navigation. Note that you aren't reading the Ethereum blockchain directly in SQL, you are just reading the abstraction layer and `index` that ABW builds on top of Ethereum.