Csdrhrt

It appears that the Halacha does not emphasize the importance of actually "sending" the Manos, they can be handed or eaten in place.

Moreover, the word לשלח is used in the Torah as "to expel", e.g. Adam was expelled from Eden or a divorced woman is "expelled" from her husband and its usage here is strange.

Why in the Meggila the action of giving out Manos is called specifically Mishloach - does it have to be far away, does it have to be by a messenger or else?

Of course, this question is based on the assumption that the Sages chose the words very carefully, and every word hints on specific applications.

There is a teshuva of the Binyan Tzion which is often quoted about this issue, in Siman #44.

He explains that the language of שליחות is to indicate that the sending itself is enough, even if the recipient does not end up receiving or accepting the gift (as per the psak of the Rema, O.C. 695):

ולענ"ד טעם המהר"י ברין ורמ"א כמו שכתוב "ומשלוח מנות "
ולא כתיב "ונתון מנות " כמו דכתיב "ומתנות לאביונים ," דלשון
נתינה שייך גבי מנות כדכתיב "ונתן לפנינה וגו' מנות ולחנה יתן
מנה אחת אפים ," מזה נראה דלא הקפיד הכתוב אלא על
השילוח דהיינו שיוצא מן המשלח

He also adds on that we don't find any poskim who say that משלוח מנות specifically require sending, and personal delivery is sufficient, which he sees as support to his claim that the point of שליחות is to indicate that this is all that is required (as opposed to מתנות לאביונים, which he asserts requires the poor person to actually receive and accept it). He does, however, conclude that it may be better to send it via a messenger, though:

ומכ"מ אולי לכתחלה טוב יותר
לשלוח המנות ע"י אחר