no
If becoming weaker is a way to improve, then yes, you did.
sure
What if I get to 455 again but this time at 165 lbs? Are you still gonna tell me I didn't improve? Lol
OP, yes, you did slightly improve depending on your definition.
Wilks at 455@205 = ~129
Wilks at 415@165 = ~134
Even by powerlifting standards, you improved. You would win best lifter if it was just you competing against your old self.