.The first thing in the garden that is not good is that "the man should be alone".
It should be remembered that this is happening during creation week on day six. It is an expanded view of the events of that day. Any other view invites the imagination of man which is wicked from his youth, to invent all kinds of evil to add into the scripture for interpretation purposes.
Why was he suddenly alone?
He wasn't 'suddenly' alone. He was the only one created at this point.
Had he already separated himself from God?
You realize that your suggesting Adam sinned before Eve was made which is in great error. To separate oneself from God is to die. Death comes by sin. Your being fed nonsense from a spirit which is not of God.
Is it possible that marriage is a picture of the relationship Adam originally had with God?
Ephesians 5:31 For this cause shall a man leave his father and mother, and shall be joined unto his wife, and they two shall be one flesh.
Ephesians 5:32This is a great mystery: but I speak concerning Christ and the church.
It is also a picture of the oneness of Christ and all his church.
His church is that woman in proverbs 31.At least we are supposed to be.
That makes sense to me,the command structure is only needed for efficiency and direction.It also prevents manipulation from either their children or from the outside world.
Marriage is a picture of Christ and the church,we give Christ the final authority.
I have been married for 29 years and my wife knows what I would do or say in almost any situation.You would think after 2000 years the bride would know him a little better but God's timing is different than ours.
Also if the two have a child then technically the two have become one flesh.
Seeing as your foundation that you set in the beginning was based upon imaginary thinking leading to error, there is no further need to address what follows.
May God through his spirit guide you into all truth,
In Jesus Name,
Gary