To answer the question directly: as far as I can tell, it effectively is flowery language that doesn't add meaning - Xについても is barely distinguishable from just Xも. The ついて here is an expression for "regarding", but a topic-marking particle (も or は) already more or less has that function.
Let's consider the clause by itself.
First, we tokenize by looking for complete words (individual kanji with or without okurigana, or kanji compounds, or recognizable sequences of katakana or hiragana) and particles:
被害 を 免れた 千人 ほど の 住民 に ついて も
Jisho can help with this process; for example, if you try looking for the part you bolded, it will be broken down into について and も, and also give you a dictionary definition for an expression. That helps understand which つく we're talking about, but it isn't perfect grammatically. We know from context that に is a particle. But the search helps us understand that も is a particle here as well, and that ついて is atomic - we can't consider the meaning of ても because that isn't how the sentence breaks down. (Similarly, there isn't really a verb "に付く" as you proposed; there is 付く preceded by a に-marked "indirect object".
Next, accumulate parts left to right:
被害 - damage, を-marked
免れた - simple past of 免れる, to escape;
thus 被害を免れた is "damage was avoided", or rather (since it's active) " avoided damage".
千人ほど - about a thousand people (ほど is listed as a particle, but it might be easier to think of here as a noun suffix)
Now we have a stand-alone clause immediately preceding a noun; thus it's attributive, describing the noun. 被害を免れた千人ほど is "about a thousand people who avoided damage".
の - we already have a noun, so this can't be a nominalizer; we just gave a fairly in-depth description of that noun, so naturally we're using it to categorize. That is: we're about to have something which can be described as "about a thousand people who avoided damage".
住民 - citizens. Thus: "the citizens, about a thousand in number, who avoided damage." (It might seem redundant to describe the citizens as people; the idea here is that 人 is a counter for people.)
Now to the meat of it: that group is the indirect object of つく; then the verb is put into the connective te-form; then all of that is a も topic for the remainder of the sentence. The つく used in expressions like this is 就く; but this usage is idiomatic, and normally written in kana. The sense - as I understand it - is that the reader metaphorically "departs" towards the (に-marked) concept described. (It's not really any weirder than the natural English translation of "regarding"; after all, you aren't physically looking at anything!) We use the te-form as a nominalizer here (something like a gerund in English; whereas when we use the te-form to connect to another verb, it's more like a gerundive).
Thus: "regarding, as well, the thousand or so citizens who avoided damage".
For the complete sentence, I get something like: "Although there had been little damage to the south side of the town, as for the thousand or so citizens who emerged unscathed, their departure from the south followed soon thereafter as well.". (More literally for the first part: "Although, as regards the south side of the town, the damage was slight,".) The "as well" should refer to the citizens rather than the departure, but the sentence wants to talk about the departure rather than saying that the citizens departed; it's difficult to capture that in English.