Besides his desire for consistency, there is a subtle liturgical distinction that your priest is trying to make here. Before the consecration, Christ is not yet present on the altar; after the consecration, he is present. That is why the preferred gesture of reverence to an altar on which Christ is not yet present is a bow – from the waist, not the head – and not a genuflection. Genuflection, a deeper form of reverence, is saved for when Christ is present on the altar (e.g., during eucharistic adoration) and for passing in front of a tabernacle.
Your priest is correct though that consistency of reverential gestures during the liturgy is important, particularly among those who are serving during the Mass in capacities such as extraordinary minister of holy Communion, lector, and altar server. Those privileged to serve in such capacities act as examples of obedience for the congregation; and, by avoiding inconsistency, refrain from drawing undue attention to themselves during the Mass.
In answer to your questions:
*]If you are acting as a lector, you should observe the reverential gestures your priest has asked you to follow. In this case, it appears that he wants you to bow to the altar before approaching the lectern. As the Liturgy of the Word occurs before the Liturgy of the Eucharist, meaning that Christ is not yet present, the gesture the priest is requesting is correct.
*]Genuflection before entering a pew depends on whether the tabernacle is visible. If you can see the tabernacle from your pew, you may turn toward it and genuflect before entering the pew. If not, then you should bow to the altar. As for whether such a gesture “suffices” for the rest of the Mass, such a gesture is not intended for that purpose. It is simply a gesture of reverence as you enter the nave of the church and is intended, in a certain sense, as a means of greeting Christ.[/LIST]Recommended reading:
The Struggle for Uniformity in the Liturgy by Kenneth D. Whitehead
Mass Appeal by Jimmy Akin