I think that your question is hard to follow, so I'll paraphrase it before answering my own paraphrase! Note that I have changed your citation of 1, 2, and 3 because you do not have them parenthesized even though you seemed to be suggesting that they should be!
I am writing for a publication that adopts a citation style that uses inline parenthesized or bracketed numerals, such as ... as stated in the original source . Some of the material that I want to quote at length uses an identical style, and some of that quoted material includes in-line parenthesized or bracketed citations. For historiographic reasons I want to reproduce the original quoted text exactly as it was written, without altering the appearance of the original in-line parenthesized or bracketed citations. A problem then arises when the quoted material itself ends with something like ... the world is flat  and I need to cite the source of those words with my own in-line parenthesized or bracketed citation. The result could potentially read ... the world is flat  , where I have used bold overall to indicate the text as it would end up appearing, and the bold-italicised  to indicate my own citation of the source of the quotation ... the world is flat . What is a sensible way of dealing with this problem?
I hope I have understood your question correctly and that my paraphrase does not deviate too far from something useful.
It's an interesting problem but not that unusual. For example, in this question, the OP wants to use APA style to cite a portion of text that, itself, might potentially include the APA referencing from the original. In fact, it arises whenever the quoted text includes in-line citations that you want to keep and the citation style of the original is identical with the in-line citation style you are using for your own writing. Imagine doing what you're describing with a clash of superscripted citation styles!
I'm assume that you can't, or don't want to, put the quoted material inside quotation marks. If you can, then that provides an obvious way of demarcating the original from your own in-line citation.
A digression ... I have yet to come across a copy-editor (and hope I never do) who is so insistent on in-house style that they are unwilling to make concessions in the face of absurdities that would confuse a reader.
With that in mind, I'd look for some minimalist way of locally but consistently altering your own in-line citations to distinguish them from the citations in the original source. For example, you could adopt a double bracketed style such as ... the world is flat  [], a supercripted bracketed style such as ... the world is flat  , or some other simple variation. I prefer the visual effect of the superscripted bracketed source reference but whatever you do, I would choose something that emphasizes clarity and readability above absolute consistency.