Hello and thank you for your detailed question.
It is clear you want the absolute best for Freddie.
Giant dogs develop slower than their peers and it takes from 18-24 months for their skeleton and muscles to fully develop.
This paper is one I refer to often for my clients:
We generally wait later in certain breeds such as the Golden Retriever and Rottie due to increased risk of cruciate disease, hip dysplasia and bone cancer in early neutering.
Whether or not this can be extrapolated to other large breeds is unknown.
Due to the data we have, I advise giant breeds wait until 18 months.
HOWEVER, this is dependent on the individual. Given all you've said about your recent experiences, Freddie is now a candidate for neutering and you may find it helps with his training and reduces the incidence of things like humping and licking.
In your place, I would neuter now if this behaviour is becoming a nuisance (to you, other people, or to Freddie himself) or wait a few months if not.