Index creation with multiple columns - should I combine as many as possible?
Based on those 3 specific recommendations, I would use

CREATE INDEX [IX_Tbl_ContractId_OpenClosedStatus] ON [tbl]
([ContractId], [OpenClosedStatus]) INCLUDE ([Id], [ClientId], [DateNextDeadline],[StringID])


The equality/inequality columns are the same, which is the bigger part.  SQL Server should use this for any queries that have all or a subset of those Included cols. 

And of course, you run this through a rigorous set of test queries to verify :)