OK, so Texas is really not vigilant about removing signs when they decommission a route then. But, if it's decommissioned it's decommissioned, so I'd say leave it as is.
Spur 303 I'm fine with leaving as is as well given that the official map shows it ending at Belt Line Rd.
Got another one for your consideraton, though.
TX 121: signage has it following a surface alingnment through Lewisville,
the grid map shows this as "121H". I'm not entirely sure what to make of that but it certainly appears 121 should be routed that way.
This would leave part of the Sam Rayburn Tollway with no number, but that could be put in usasf.