The catalysts states ALL reapers are destroyed with the destroy option. If the crucible explosions could be extragalactic then they would not require mass relays. It would just explode and send the energy out but it uses the MASS RELAYS to blanket the galaxy that is what we see. If the energy is only within the milky way and all reapers die with the destroy option then the reapers are all within the galaxy. Its rather simple. All cats have four limbs. Snuffles is a cat. Therefore snuffles has four limbs. All reapers are destroyed. The energy is confined to the milky way. Therefore the reapers are all in the milky way.
Speaking evidentiary? Show me ONE scrap of evidence that shows them anywhere but the milky way. the Dark space relay is twined with the citadel so even when they are hibernating they are tied to the milky way galaxy. There isn't a single piece of evidence that the reapers care about life beyond the milky way.
Your entire post accidentally supports what I have been saying with one exception, and that is your first sentence. Unfortunately, I can't remember if Star Brat actually specifies that ALL Reapers will die. Even if he did, this does not necessarily mean he is speaking the truth, or if by "all" he means all those relevant to us in the Milky Way.
As far as your second paragrapph, you are just repeating things that I have said, and spitting out a conclusion based, again, on presumptions you are making. You assume that there is only one Citadel, for instance, and not others in otehr galaxies.
You are also missing a key component of my comments: I never said they DID go to other galaxies, but that they did not because the writers have said so (perhaps not in so many words, but we can be fairly confident they are done with the Reapers). My point is simply that if we can go to Andromeda, then the Reapers easily could have gone there. And this only indicates more ineptitude from the writers. What they have done is not so much avoid the issues they created in the ME trilogy, but exacerbate them, and make the whole story and the Reapers in general even more silly than they were before.
Furthermore, like I said but you seemed to have ignored, it is impossible for there to be evidence of the Reapers going to other galaxies, because the writers never considered that prior to ME:A. Therefore, we can only extrapolate and make assumptions based on information in the trilogy that was never built around the notion of the Reapers traveling intergalactically.
In short, ME is getting rebooted, because the ramifications of us going to Andromeda, vis-a-vis the Reapers, are being ignored. Basically, the writers wanted to reboot the franchise to keep name recognition, but wanted the ability to say that they "respect our choices." So they simply are ignoring the trilogy, save for, perhaps, some slight mention of them to give some illusion that the trilogy actually matters anymore. Like I have said before, ME:A is a stupid attempt to hand wave away the Reapers, the trilogy, its stupid endings, while preserving the brand name in an attempt to cash in on it. What they should have done, is retire the franchise, it is the only correct choice.