1) The rite of ordination seems to indicate that the deaconess is ordained to the work of service whereas the deacon is ordained to assist in the service of the most pure mysteries. Doesn't this make the deacon and deaconess fundamentally different in their role?
Though they serve in different capacities, the role of male and female deacons is not ontologically different. They were both appointed by the Apostles to serve the Church, primarily in the role of helping the widows and orphans, helping the poor and sick by distributing alms, etc. I think that the scripture is clear that, regardless of however the role may have developed in regards to their role in the Divine Services, the primary role for deacons is and continues to be this. Women deacons are ordained in the altar, but like readers who only wear the short-phelonion for a very short time and are then traditionally only used for service in the altar whenever there is a need, women deacon's liturgical service is likewise short. This is particularly for sake of propriety in following the exhortation by St. Paul in regards to male and female use of gifts in the liturgy. (Noter: women are permitted, by apostolic approval by their bishop of course, to serve in the altar when there are no men present as in the case of a women's monastery, but never to fill the role of the priest or bishop). They are coordinators, the hands of the bishop to serve the poor and downtrodden and subsequently keep order in the local parish church (this is also, ironically, why the male deacon stands before the Royal Doors on the ambo during the litanies appointed for him in the Divine Services; at one time to lead the people in prayer and at another to protect and guard the Holy Gifts as a sentry).
2) Why isn't the ordained deaconess able to be ordained as a priest? I understand that there is no Tradition for this, but sacramentally, since the deaconess has received the sacrament of holy orders, isn't this considered the same sacrament as the priest and Bishop, only to a different degree?
The deacon(ess) is different because his/her role is ontologically different than that of the priest. Though they all possess Holy Orders, the Orders that they possess differ.
A bishop is the icon of God the Father. Only through him can ordinations be made, rites approved, discipline be established, etc in the same way that it is only through the Father's will that the Word speaks and the Spirit is breathed and proceeds from the Father. This is because the Will of the Father is the same will as the Son and the Spirit for they are united under the monarchical headship of the Father. As St. Ignatius of Antioch says "Where the Bishop is, there is the Church."
The priest lifts up and makes sacrifice to God the Father as a servant of the Bishop. He is the ontological icon of Jesus Christ, the Word made Flesh. Nothing that he does, can he do apart from his Father. In the same way, the priest does not ordain, consecrate chrism, approve rites, establish discipline for his flock but in all things must rely on the will of the Bishop (who being in the icon of the Father has the role of Creator). They share many similarities since as the Lord says, "truly, truly, I say to you, the Son can do nothing of his own accord, but only what he sees the Father doing; for whatever he does, that the Son does likewise." Also, the priest has been deligated certain prerogatives by the Bishop such as serving the liturgy in his place, hearing confessions for him, administering the chrism which he has consecrated etc because as the Scripture says of Christ "The Father judges no one, but has given all judgment to the Son, that all may honor the Son, even as they honor the Father. He who does not honor the Son does not honor the Father who sent him." As he is the Son of the Father, he cannot, by ontological nature be a daughter. Hence, we have an all male priesthood and episcopacy. Otherwise the icon would be corrupted and the balance of roles skewed (regardless of how much some women in the feminist movement would love to usurp the role of men where it is not physically allotted to them, there are biological and, we would argue spiritual, differences. Complimentary differences, but differences none-the-less, which I will get into when I speak of the deacon(ess).
The deacon, likewise continues to share in the possession of Holy Orders. The particular role of the deacon as expressed above is to serve and comfort. For this same reason we address the Holy Spirit as the "comforter." The Holy Spirit is also referred to as The Helper. Because women, in the role given to them by God in the garden of Eden are also referred to primarily as helpers/assistants to men (albeit while being equal to them in dignity as God's creations, just as the Holy Spirit is equal in essence to God the Father and God the Son) and having proceeded from man by the taking of a rib (as the Holy Spirit proceeds from the Father as like a breath), it can be considered proper for females to serve in the role of deaconesses while never having the possibility of being elevated to the priesthood or episcopacy.
Unfortunately Holy Orders have come to be understood as an order of power. Bishop, then Priest, then Deacon. This is not the case. They all equally share in the ministry of the apostles and are all equally an icon of the Father, Son and Holy Spirit just as God is One, and undivided; but they also possess different ontological roles that compliment and support one another.