Washington drafted Seastrunk in the sixth round last year but cut him at the end of the preseason. He split 2014 on the practice squads of Carolina and Tennessee before the Titans signed him to a futures contract after the season. He was waived May 18.
Seastrunk was a high school star in Temple, not far from Baylor's Waco campus, before going to Oregon. He later joined the Bears as a transfer.
Jackson, who went to Wake Forest, signed with Detroit as an undrafted free agent last year. He was on the practice squads in Cincinnati, Washington and Oakland last season.
Dallas also waived running back Synjyn Days.
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