Unlike English "to be -ing" form, Japanese ている-form can describe a habitual action or something that is always true.
When is Vている the continuation of action and when is it the continuation of state?
古くなった細胞は毎日死んでいる。 Old cells die every day. (not are dying or have died)
毎週大阪に行っている。 I go to Osaka every week. (not am going or have ...
誘われて is the passive -te form, usually understood by the final verb. However, this -te form (as a standard grammatical construct) may simply end the first part of a compound sentence, such as your example:
and, as it were, the same is true of first sentence of KAWAKAMI Hiromi's short story "Kamisama"
In the above two cases, 「に」and「で」are exchangeable with very little changes in nuance. You can say 「日本人の会話では下の例のように...」or「日本語の会話には、文の倒置も...」.
When you say「AにはB」, you are just describing that A has the attribute B. On the other hand, by saying「AではB」, you are distinguishing A from other subjects by the fact B is established in A.
If you think that "「～けど」や「～...
含まれ(る) here is passive. It literally means "In this, is sugar contained?"
is incorrect. You could instead say:
which literally means "Does this contain sugar?"
Sometimes the N2 in that pattern is omitted, either if it is clearly understood or if the causal agent is not known or is unclear. In your sentence, N1 is understood to be the speaker, N3 is 荷物, and N2 is omitted. If you imagine that N2 is something like 荷物係 (baggage handler) then it might make more sense to you.