Has the aforementioned marriage been completed, or is there a deficiency that invalidates it, knowing that there was a guardian, two witnesses, offer and acceptance, and prior agreement on the dowry and deferred dowry?

It appears that you have adopted the view of those who consider the abandonment of prayer as an act of absolute disbelief, thereby transferring guardianship from the father to the brother, based on the principle that a disbeliever cannot be a guardian over a Muslim woman. Accordingly, the contract is valid, and it is not affected by the fact that the offer and acceptance were in a language other than Arabic, nor by the absence of the dowry mention in the contract, nor by the fact that the wife's brother — who is not the guardian — was a witness.