Generally speaking, weapon drop limits are the same as carriage limits as far as speed goes. It makes no sense to approach a target at high speed, then slow down to drop a weapon. Desired carriage and separation limits are specified by the customer, say USAF, then the airplane and weapon are designed and tested to those limits. Nothing says the weapon cannot be dropped at higher speeds, but it would take additional analysis and test to verify it.
So if you know the carriage limit, you probably know the separation limit. If you don't know the carriage limit, then you don't need to know the separation limit.