1 & 2.
From the 2004 Instruction Redemptionis Sacramentum:
“[74.] If the need arises for the gathered faithful to be given instruction or testimony by a layperson in a Church concerning the Christian life, it is altogether preferable that this be done outside Mass. Nevertheless, for serious reasons it is permissible that this type of instruction or testimony be given after the Priest has proclaimed the Prayer after Communion. This should not become a regular practice, however. Furthermore, these instructions and testimony should not be of such a nature that they could be confused with the homily, nor is it permissible to dispense with the homily on their account.”
From the 2002 General Instruction of the Roman Missal (GIRM) approved for the USA, which can be accessed from
romanrite.com/girm.html :
“154. … The priest may give the sign of peace to the ministers but always remains within the sanctuary, so as not to disturb the celebration. In the dioceses of the United States of America, for a good reason, on special occasions (for example, in the case of a funeral, a wedding, or when civic leaders are present) the priest may offer the sign of peace to a few of the faithful near the sanctuary.”
- I think the homily location is fairly flexible, depending on what is regarded as suitable in a given situation.
From the 2002 GIRM: “136. The priest, standing at the chair or at the ambo itself or, when appropriate, in another suitable place, gives the homily. When the homily is completed, a period of silence may be observed.”
- Regarding personal messages from the priest. It discusses “explanations” in the GIRM:
“31. It is also up to the priest, in the exercise of his office of presiding over the gathered assembly, to offer certain explanations that are foreseen in the rite itself. Where it is indicated in the rubrics, the celebrant is permitted to adapt them somewhat in order that they respond to the understanding of those participating. However, he should always take care to keep to the sense of the text given in the Missal and to express them succinctly. The presiding priest is also to direct the word of God and to impart the final blessing. In addition, he may give the faithful a very brief introduction to the Mass of the day
(after the initial Greeting and before the Act of Penitence), to the Liturgy of the Word (before the readings), and to the Eucharistic Prayer (before the Preface), though never during the Eucharistic Prayer itself; he may also make concluding comments to the entire sacred action before the dismissal.”
Giving “explanations” is also described as part of the role of the commentator (in n. 105(b)) and the deacon 171(d):
“Guides the faithful by appropriate introductions and explanations, and announces the intentions of the Prayer of the Faithful;”
The Introduction to the Lectionary for Mass has:
“15. There may be concise introductions before the readings, especially the first. The style proper to such comments must be respected, that is, they must be simple, faithful to the text, brief, well prepared, and properly varied to suit the text they introduce.”