1,2,3.   look in Books online.  You can add/drop articles/columns from existing publications.  You do not need to break replication.

         SP_AddArticle, SP_DropArticle to add/drop tables

         SP_ReplAddColumn, SP_ReplDropColumn to add/drop columns

4.   ...

Use SP_AddArticle - see Books Online for options.  This needs to be run on the publisher.  You do not need to create a new Snapshot

You broke the ownership change by using dynamic SQL. Try the following:

create proc lsp_deleteorders @OrderID int

as

Update orders

set active = 0

where OrderID = @orderID

You...