A Data Space is either a Filegroup or a Partition Scheme. Everything showing in your result with a Data Space Name that isn't a filegroup (or has a data_space_id that doesn't map to a filegroup_id in sys.filegroups) is partitioned, and must be moved off the partitions before you can drop the Partition Function and Scheme.
You will need to re-CREATE each non-filegroup index on a filegroup instead of the partition (use CREATE INDEX even though the index already exists; include WITH (DROP_EXISTING = ON))
CREATE [CLUSTERED|NONCLUSTERED] INDEX[...] ON [<table_name>](col, col, col...)
WITH (DROP_EXISTING = ON, <other_index_option>, <other_index_option>, <other_index_option>, ...)