i think the problem is with the OLEDB Connection.Check this
thread.It suggest to
"Change the Crystal report to use an OLE DB datasource rather than the SAP Business One data source."
and for the second question you are facing just click on ok button after finishing the datatable linking part.Then drag and drop only neccesary field to the report you want to display.The tutorial you have gone through is an old version of CR.
This is a good
article you to follow