Was Adam fully human?
It depends what is meant by “fully human” in your question.
If you are asking “Was Adam ‘fully human’ in the ontological sense”, then my answer is yes.
If you are asking “Did Adam experience all that we humans today experience” then no he did not.
Was Adam born via a womb? No. Was he ever a fertilized egg? No. Etc.
John 6:63
The Spirit gives life; the flesh profits nothing;
the words that I have spoken unto you, they are Spirit and they are life.