No, the priest should not pour water in the cruet of wine.
No, I do not see it as necessary to add water to every chalice of wine. I am not aware of detailed instructions on this in the liturgical books.
A priest should not add the water and wine at the credence table. A minister should present the cruets to him at the altar.
A deacon may add the wine and water to the chalice at the credence table.
From the 2002 General Instruction of the Roman Missal (GIRM) approved for the USA, which can be accessed from
romanrite.com/girm.html …
In the section “Mass without a Deacon”:
“142. After this, as the minister presents the cruets, the priest stands at the side of the altar and pours wine and a little water into the chalice, saying quietly,
Per huius aquae (By the mystery of this water). He returns to the middle of the altar, takes the chalice with both hands, raises it a little, and says quietly, *Benedictus es, Domine (Blessed are you, Lord). *Then he places the chalice on the corporal and covers it with a pall, as appropriate.
If, however, there is no Offertory chant and the organ is not played, in the presentation of the bread and wine the priest may say the formulas of blessing aloud, to which the people make the acclamation,
Benedictus Deus in saecula (Blessed be God for ever).”
In the section “Mass with a Deacon”:
“178. After the Prayer of the Faithful, while the priest remains at the chair, the deacon prepares the altar, assisted by the acolyte, but it is the deacon’s place to take care of the sacred vessels himself. He also assists the priest in receiving the people’s gifts. Next, he hands the priest the paten with the bread to be consecrated, pours wine and a little water into the chalice, saying quietly,* Per huius aquae (By the mystery of this water)*, and after this presents the chalice to the priest. He may also carry out the preparation of the chalice at the credence table. If incense is used, the deacon assists the priest during the incensation of the gifts, the cross, and the altar; afterwards, the deacon himself or the acolyte incenses the priest and the people.”
In the section “Mass at Which Only One Minister Participates” it has:
“255. Before Mass, the necessary vessels are prepared either at the credence table or on the righthand side of the altar.”
This is different to a normal Mass, when the vessels are to be at the credence table. In the description of Mass With Only One Minister it has, “265. In the Liturgy of the Eucharist, everything is done as in a Mass with a congregation, with the following exceptions.” No exception is given to the method of adding the water and wine to the chalice.
GIRM 306-308 has a detailed list of what should be put on the altar. It does not include the cruets with the water and wine.