It is clear from the writings of the Early Church Fathers that the early church believed that the bread and the wine became the body and blood of Christ. For example:
"For not as common bread and common drink do we receive these; but in like manner as Jesus Christ our Saviour, having been made flesh by the Word of God, had both flesh and blood for our salvation, so likewise have we been taught that the food which is blessed by the prayer of His word, and from which our blood and flesh by transmutation are nourished, is the flesh and blood of that Jesus who was made flesh."-Justin Martyr
"I have no delight in corruptible food, nor in the pleasures of this life. I desire the bread of God, the heavenly bread, the bread of life, which is the flesh of Jesus Christ, the Son of God, who became afterwards of the seed of David and Abraham; and I desire the drink of God, namely His blood, which is incorruptible love and eternal life." St. Ignatius of Antioch Letter to the Romans written around 107 A.D. about the same time as the Didache.
Also, the early Christians worshipped on Sunday because that was the day of the week that Christ was resurrected. That is why they called it the Lord's Day.
"If, therefore, those who were brought up in the ancient order of things have come to the possession of a new hope, no longer observing the Sabbath, but living in the observance of the Lord's Day, on which also our life has sprung up again by Him and by His death--" St. Ignatius of Antioch Letter to the Magnesians written around 107 A.D.